Merge pull request #2127 from tananaev/refactor

Move device id to a session

115 files changed, 867 insertions, 497 deletions

diff --git a/src/org/traccar/BaseProtocolDecoder.java b/src/org/traccar/BaseProtocolDecoder.java
index 59205bc6f..46832a4ca 100644
--- a/src/org/traccar/BaseProtocolDecoder.java
+++ b/src/org/traccar/BaseProtocolDecoder.java
@@ -16,6 +16,7 @@
 package org.traccar;
 
 import org.jboss.netty.channel.Channel;
+import org.jboss.netty.channel.socket.DatagramChannel;
 import org.traccar.helper.Log;
 import org.traccar.model.Device;
 import org.traccar.model.Position;
@@ -23,6 +24,8 @@ import org.traccar.model.Position;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.util.Date;
+import java.util.HashMap;
+import java.util.Map;
 
 public abstract class BaseProtocolDecoder extends ExtendedObjectDecoder {
 
@@ -32,47 +35,69 @@ public abstract class BaseProtocolDecoder extends ExtendedObjectDecoder {
         return protocol.getName();
     }
 
-    private long deviceId;
-
-    public boolean hasDeviceId() {
-        return deviceId != 0;
-    }
-
-    public long getDeviceId() {
+    private DeviceSession channelDeviceSession; // connection-based protocols
+    private Map<SocketAddress, DeviceSession> addressDeviceSessions = new HashMap<>(); // connectionless protocols
+
+    private long findDeviceId(SocketAddress remoteAddress, String... uniqueIds) {
+        long deviceId = 0;
+        if (uniqueIds.length > 0) {
+            try {
+                for (String uniqueId : uniqueIds) {
+                    if (uniqueId != null) {
+                        Device device = Context.getIdentityManager().getDeviceByUniqueId(uniqueId);
+                        if (device != null) {
+                            deviceId = device.getId();
+                            break;
+                        }
+                    }
+                }
+            } catch (Exception e) {
+                Log.warning(e);
+            }
+            if (deviceId == 0) {
+                StringBuilder message = new StringBuilder("Unknown device -");
+                for (String uniqueId : uniqueIds) {
+                    message.append(" ").append(uniqueId);
+                }
+                if (remoteAddress != null) {
+                    message.append(" (").append(((InetSocketAddress) remoteAddress).getHostString()).append(")");
+                }
+                Log.warning(message.toString());
+            }
+        }
         return deviceId;
     }
 
-    public boolean identify(String uniqueId, Channel channel, SocketAddress remoteAddress, boolean logWarning) {
-        try {
-            Device device = Context.getIdentityManager().getDeviceByUniqueId(uniqueId);
-            if (device != null) {
-                deviceId = device.getId();
+    public DeviceSession getDeviceSession(Channel channel, SocketAddress remoteAddress, String... uniqueIds) {
+        if (channel instanceof DatagramChannel) {
+            long deviceId = findDeviceId(remoteAddress, uniqueIds);
+            DeviceSession deviceSession = addressDeviceSessions.get(remoteAddress);
+            if (deviceSession != null && (deviceSession.getDeviceId() == deviceId || uniqueIds.length == 0)) {
+                return deviceSession;
+            } else if (deviceId != 0) {
+                deviceSession = new DeviceSession(deviceId);
+                addressDeviceSessions.put(remoteAddress, deviceSession);
                 if (Context.getConnectionManager() != null) {
                     Context.getConnectionManager().addActiveDevice(deviceId, protocol, channel, remoteAddress);
                 }
-                return true;
+                return deviceSession;
             } else {
-                deviceId = 0;
-                if (logWarning) {
-                    String message = "Unknown device - " + uniqueId;
-                    if (remoteAddress != null) {
-                        message += " (" + ((InetSocketAddress) remoteAddress).getHostString() + ")";
+                return null;
+            }
+        } else {
+            if (channelDeviceSession == null) {
+                long deviceId = findDeviceId(remoteAddress, uniqueIds);
+                if (deviceId != 0) {
+                    channelDeviceSession = new DeviceSession(deviceId);
+                    if (Context.getConnectionManager() != null) {
+                        Context.getConnectionManager().addActiveDevice(deviceId, protocol, channel, remoteAddress);
                     }
-                    Log.warning(message);
                 }
-                return false;
             }
-        } catch (Exception error) {
-            deviceId = 0;
-            Log.warning(error);
-            return false;
+            return channelDeviceSession;
         }
     }
 
-    public boolean identify(String uniqueId, Channel channel, SocketAddress remoteAddress) {
-        return identify(uniqueId, channel, remoteAddress, true);
-    }
-
     public BaseProtocolDecoder(Protocol protocol) {
         this.protocol = protocol;
     }
@@ -104,17 +129,19 @@ public abstract class BaseProtocolDecoder extends ExtendedObjectDecoder {
 
     @Override
     protected void onMessageEvent(Channel channel, SocketAddress remoteAddress, Object msg) {
-        if (hasDeviceId()) {
-            Context.getConnectionManager().updateDevice(deviceId, Device.STATUS_ONLINE, new Date());
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession != null) {
+            Context.getConnectionManager().updateDevice(deviceSession.getDeviceId(), Device.STATUS_ONLINE, new Date());
         }
     }
 
     @Override
     protected Object handleEmptyMessage(Channel channel, SocketAddress remoteAddress, Object msg) {
-        if (Context.getConfig().getBoolean("database.saveEmpty") && hasDeviceId()) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (Context.getConfig().getBoolean("database.saveEmpty") && deviceSession != null) {
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
             getLastLocation(position, null);
             return position;
         } else {
diff --git a/src/org/traccar/DeviceSession.java b/src/org/traccar/DeviceSession.java
new file mode 100644
index 000000000..5e2686f23
--- /dev/null
+++ b/src/org/traccar/DeviceSession.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2016 Anton Tananaev (anton.tananaev@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.traccar;
+
+public class DeviceSession {
+
+    private final long deviceId;
+
+    public DeviceSession(long deviceId) {
+        this.deviceId = deviceId;
+    }
+
+    public long getDeviceId() {
+        return deviceId;
+    }
+
+}
diff --git a/src/org/traccar/protocol/AdmProtocolDecoder.java b/src/org/traccar/protocol/AdmProtocolDecoder.java
index dd089e8e3..e234e3f0b 100644
--- a/src/org/traccar/protocol/AdmProtocolDecoder.java
+++ b/src/org/traccar/protocol/AdmProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -47,15 +48,23 @@ public class AdmProtocolDecoder extends BaseProtocolDecoder {
 
         int type = buf.readUnsignedByte();
 
+        DeviceSession deviceSession;
         if (type == MSG_IMEI) {
-            identify(buf.toString(buf.readerIndex(), 15, StandardCharsets.US_ASCII), channel, remoteAddress);
+            deviceSession = getDeviceSession(
+                    channel, remoteAddress, buf.readBytes(15).toString(StandardCharsets.US_ASCII));
+        } else {
+            deviceSession = getDeviceSession(channel, remoteAddress);
         }
 
-        if (hasDeviceId() && BitUtil.to(type, 2) == 0) {
+        if (deviceSession == null) {
+            return null;
+        }
+
+        if (BitUtil.to(type, 2) == 0) {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             buf.readUnsignedByte(); // firmware version
             buf.readUnsignedShort(); // index
diff --git a/src/org/traccar/protocol/ApelProtocolDecoder.java b/src/org/traccar/protocol/ApelProtocolDecoder.java
index fb473be1e..f10c4b5b1 100644
--- a/src/org/traccar/protocol/ApelProtocolDecoder.java
+++ b/src/org/traccar/protocol/ApelProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -110,7 +111,7 @@ public class ApelProtocolDecoder extends BaseProtocolDecoder {
             int length = buf.readUnsignedShort();
             buf.skipBytes(length);
             length = buf.readUnsignedShort();
-            identify(buf.readBytes(length).toString(StandardCharsets.US_ASCII), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, buf.readBytes(length).toString(StandardCharsets.US_ASCII));
 
         } else if (type == MSG_LAST_LOG_INDEX) {
 
@@ -120,8 +121,12 @@ public class ApelProtocolDecoder extends BaseProtocolDecoder {
                 requestArchive(channel);
             }
 
-        } else if (hasDeviceId()
-                && (type == MSG_CURRENT_GPS_DATA || type == MSG_STATE_FULL_INFO_T104 || type == MSG_LOG_RECORDS)) {
+        } else if (type == MSG_CURRENT_GPS_DATA || type == MSG_STATE_FULL_INFO_T104 || type == MSG_LOG_RECORDS) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             List<Position> positions = new LinkedList<>();
 
@@ -133,7 +138,7 @@ public class ApelProtocolDecoder extends BaseProtocolDecoder {
             for (int j = 0; j < recordCount; j++) {
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 int subtype = type;
                 if (type == MSG_LOG_RECORDS) {
diff --git a/src/org/traccar/protocol/AplicomProtocolDecoder.java b/src/org/traccar/protocol/AplicomProtocolDecoder.java
index 70e5d7d71..ff5a1aa20 100644
--- a/src/org/traccar/protocol/AplicomProtocolDecoder.java
+++ b/src/org/traccar/protocol/AplicomProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.Log;
 import org.traccar.helper.UnitsConverter;
@@ -214,11 +215,11 @@ public class AplicomProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
-
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int event = buf.readUnsignedByte();
         position.set(Position.KEY_EVENT, event);
diff --git a/src/org/traccar/protocol/AppelloProtocolDecoder.java b/src/org/traccar/protocol/AppelloProtocolDecoder.java
index bc3e7885d..4535464ed 100755
--- a/src/org/traccar/protocol/AppelloProtocolDecoder.java
+++ b/src/org/traccar/protocol/AppelloProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -60,13 +61,14 @@ public class AppelloProtocolDecoder extends BaseProtocolDecoder {
         }
 
         String imei = parser.next();
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (parser.hasNext(6)) {
             DateBuilder dateBuilder = new DateBuilder()
diff --git a/src/org/traccar/protocol/AquilaProtocolDecoder.java b/src/org/traccar/protocol/AquilaProtocolDecoder.java
index 52f6c61a4..514448d9b 100644
--- a/src/org/traccar/protocol/AquilaProtocolDecoder.java
+++ b/src/org/traccar/protocol/AquilaProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -80,10 +81,11 @@ public class AquilaProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_EVENT, parser.nextInt());
 
diff --git a/src/org/traccar/protocol/Ardi01ProtocolDecoder.java b/src/org/traccar/protocol/Ardi01ProtocolDecoder.java
index 1dcfc51bf..1eaa65d84 100644
--- a/src/org/traccar/protocol/Ardi01ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Ardi01ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -59,10 +60,11 @@ public class Ardi01ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/ArknavProtocolDecoder.java b/src/org/traccar/protocol/ArknavProtocolDecoder.java
index 5e633c198..6c6edc905 100644
--- a/src/org/traccar/protocol/ArknavProtocolDecoder.java
+++ b/src/org/traccar/protocol/ArknavProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -61,10 +62,11 @@ public class ArknavProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.next().equals("A"));
         position.setLatitude(parser.nextCoordinate());
diff --git a/src/org/traccar/protocol/ArnaviProtocolDecoder.java b/src/org/traccar/protocol/ArnaviProtocolDecoder.java
index 46728c53e..f7e146172 100644
--- a/src/org/traccar/protocol/ArnaviProtocolDecoder.java
+++ b/src/org/traccar/protocol/ArnaviProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -67,10 +68,11 @@ public class ArnaviProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_INDEX, parser.nextInt());
         position.set(Position.KEY_POWER, parser.nextInt() * 0.01);
diff --git a/src/org/traccar/protocol/AstraProtocolDecoder.java b/src/org/traccar/protocol/AstraProtocolDecoder.java
index f6b4ed559..6880047a9 100644
--- a/src/org/traccar/protocol/AstraProtocolDecoder.java
+++ b/src/org/traccar/protocol/AstraProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -52,7 +53,8 @@ public class AstraProtocolDecoder extends BaseProtocolDecoder {
         buf.readUnsignedShort(); // length
 
         String imei = String.format("%08d", buf.readUnsignedInt()) + String.format("%07d", buf.readUnsignedMedium());
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -62,7 +64,7 @@ public class AstraProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             buf.readUnsignedByte(); // index
 
diff --git a/src/org/traccar/protocol/AtrackProtocolDecoder.java b/src/org/traccar/protocol/AtrackProtocolDecoder.java
index 0f1eb5f8e..60d5244a0 100644
--- a/src/org/traccar/protocol/AtrackProtocolDecoder.java
+++ b/src/org/traccar/protocol/AtrackProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -188,7 +189,8 @@ public class AtrackProtocolDecoder extends BaseProtocolDecoder {
         int index = buf.readUnsignedShort();
 
         long id = buf.readLong();
-        if (!identify(String.valueOf(id), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(id));
+        if (deviceSession == null) {
             return null;
         }
 
@@ -200,7 +202,7 @@ public class AtrackProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             if (longDate) {
 
diff --git a/src/org/traccar/protocol/AuroProtocolDecoder.java b/src/org/traccar/protocol/AuroProtocolDecoder.java
index ff3ab5b0d..428e83f99 100644
--- a/src/org/traccar/protocol/AuroProtocolDecoder.java
+++ b/src/org/traccar/protocol/AuroProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -67,10 +68,11 @@ public class AuroProtocolDecoder extends BaseProtocolDecoder {
 
         position.set(Position.KEY_INDEX, parser.nextInt());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(true);
         position.setLongitude(parser.nextCoordinate(Parser.CoordinateFormat.HEM_DEG_MIN_MIN));
diff --git a/src/org/traccar/protocol/AutoFonProtocolDecoder.java b/src/org/traccar/protocol/AutoFonProtocolDecoder.java
index b80fd6bcb..dd0f54af0 100644
--- a/src/org/traccar/protocol/AutoFonProtocolDecoder.java
+++ b/src/org/traccar/protocol/AutoFonProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
@@ -57,11 +58,11 @@ public class AutoFonProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position decodePosition(ChannelBuffer buf, boolean history) {
+    private Position decodePosition(DeviceSession deviceSession, ChannelBuffer buf, boolean history) {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (!history) {
             buf.readUnsignedByte(); // interval
@@ -127,20 +128,27 @@ public class AutoFonProtocolDecoder extends BaseProtocolDecoder {
             }
 
             String imei = ChannelBuffers.hexDump(buf.readBytes(8)).substring(1);
-            if (!identify(imei, channel, remoteAddress)) {
-                return null;
-            }
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
 
-            if (channel != null) {
+            if (deviceSession != null && channel != null) {
                 ChannelBuffer response = ChannelBuffers.dynamicBuffer();
                 response.writeBytes("resp_crc=".getBytes(StandardCharsets.US_ASCII));
                 response.writeByte(buf.getByte(buf.writerIndex() - 1));
                 channel.write(response);
             }
 
-        } else if (type == MSG_LOCATION) {
+            return null;
+
+        }
+
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
+            return null;
+        }
+
+        if (type == MSG_LOCATION) {
 
-            return decodePosition(buf, false);
+            return decodePosition(deviceSession, buf, false);
 
         } else if (type == MSG_HISTORY) {
 
@@ -149,7 +157,7 @@ public class AutoFonProtocolDecoder extends BaseProtocolDecoder {
             List<Position> positions = new LinkedList<>();
 
             for (int i = 0; i < count; i++) {
-                positions.add(decodePosition(buf, true));
+                positions.add(decodePosition(deviceSession, buf, true));
             }
 
             return positions;
@@ -158,7 +166,7 @@ public class AutoFonProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             short status = buf.readUnsignedByte();
             position.set(Position.KEY_ALARM, BitUtil.check(status, 7));
diff --git a/src/org/traccar/protocol/Avl301ProtocolDecoder.java b/src/org/traccar/protocol/Avl301ProtocolDecoder.java
index 1f7e3470c..4d2dfe126 100644
--- a/src/org/traccar/protocol/Avl301ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Avl301ProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
 
@@ -46,7 +47,7 @@ public class Avl301ProtocolDecoder extends BaseProtocolDecoder {
     public static final int MSG_STATUS = 'H';
     public static final int MSG_GPS_LBS_STATUS = '$';
 
-    private static void sendResponse(Channel channel, int type) {
+    private void sendResponse(Channel channel, int type) {
         if (channel != null) {
             ChannelBuffer response = ChannelBuffers.directBuffer(5);
             response.writeByte('$');
@@ -69,18 +70,24 @@ public class Avl301ProtocolDecoder extends BaseProtocolDecoder {
 
         if (type == MSG_LOGIN) {
 
-            if (identify(readImei(buf), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, readImei(buf));
+            if (deviceSession == null) {
                 sendResponse(channel, type);
             }
 
-        } else if (hasDeviceId() && type == MSG_STATUS) {
+        } else if (type == MSG_STATUS) {
 
             sendResponse(channel, type);
 
-        } else if (hasDeviceId() && type == MSG_GPS_LBS_STATUS) {
+        } else if (type == MSG_GPS_LBS_STATUS) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Position position = new Position();
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
             position.setProtocol(getProtocolName());
 
             DateBuilder dateBuilder = new DateBuilder()
diff --git a/src/org/traccar/protocol/BceProtocolDecoder.java b/src/org/traccar/protocol/BceProtocolDecoder.java
index 5502de5b2..06290b6b0 100644
--- a/src/org/traccar/protocol/BceProtocolDecoder.java
+++ b/src/org/traccar/protocol/BceProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.model.Position;
 
@@ -49,7 +50,8 @@ public class BceProtocolDecoder extends BaseProtocolDecoder {
         ChannelBuffer buf = (ChannelBuffer) msg;
 
         String imei = String.format("%015d", buf.readLong());
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -65,7 +67,7 @@ public class BceProtocolDecoder extends BaseProtocolDecoder {
 
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 int structEnd = buf.readUnsignedByte() + buf.readerIndex();
 
diff --git a/src/org/traccar/protocol/BlackKiteProtocolDecoder.java b/src/org/traccar/protocol/BlackKiteProtocolDecoder.java
index 6787140e0..92179072a 100644
--- a/src/org/traccar/protocol/BlackKiteProtocolDecoder.java
+++ b/src/org/traccar/protocol/BlackKiteProtocolDecoder.java
@@ -1,6 +1,6 @@
 /*
+ * Copyright 2013 - 2016 Anton Tananaev (anton.tananaev@gmail.com)
  * Copyright 2015 Vijay Kumar (vijaykumar@zilogic.com)
- * Copyright 2013 - 2014 Anton Tananaev (anton.tananaev@gmail.com)
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,8 +20,8 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
-import org.traccar.helper.Log;
 import org.traccar.model.Position;
 
 import java.net.SocketAddress;
@@ -96,9 +96,7 @@ public class BlackKiteProtocolDecoder extends BaseProtocolDecoder {
             switch (tag) {
 
                 case TAG_IMEI:
-                    String imei = buf.toString(buf.readerIndex(), 15, StandardCharsets.US_ASCII);
-                    buf.skipBytes(imei.length());
-                    identify(imei, channel, remoteAddress);
+                    getDeviceSession(channel, remoteAddress, buf.readBytes(15).toString(StandardCharsets.US_ASCII));
                     break;
 
                 case TAG_DATE:
@@ -174,15 +172,15 @@ public class BlackKiteProtocolDecoder extends BaseProtocolDecoder {
             positions.add(position);
         }
 
-        if (!hasDeviceId()) {
-            Log.warning("Unknown device");
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
             return null;
         }
 
         sendReply(channel, buf.readUnsignedShort());
 
         for (Position p : positions) {
-            p.setDeviceId(getDeviceId());
+            p.setDeviceId(deviceSession.getDeviceId());
         }
 
         if (positions.isEmpty()) {
diff --git a/src/org/traccar/protocol/BoxProtocolDecoder.java b/src/org/traccar/protocol/BoxProtocolDecoder.java
index 480417607..f0a90ad97 100644
--- a/src/org/traccar/protocol/BoxProtocolDecoder.java
+++ b/src/org/traccar/protocol/BoxProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -57,7 +58,7 @@ public class BoxProtocolDecoder extends BaseProtocolDecoder {
 
             int index = sentence.indexOf(',', 2) + 1;
             String id = sentence.substring(index, sentence.indexOf(',', index));
-            identify(id, channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, id);
 
         } else if (sentence.startsWith("E,")) {
 
@@ -65,7 +66,12 @@ public class BoxProtocolDecoder extends BaseProtocolDecoder {
                 channel.write("A," + sentence.substring(2) + "\r");
             }
 
-        } else if (sentence.startsWith("L,") && hasDeviceId()) {
+        } else if (sentence.startsWith("L,")) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Parser parser = new Parser(PATTERN, sentence);
             if (!parser.matches()) {
@@ -73,7 +79,7 @@ public class BoxProtocolDecoder extends BaseProtocolDecoder {
             }
 
             Position position = new Position();
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
             position.setProtocol(getProtocolName());
 
             DateBuilder dateBuilder = new DateBuilder()
diff --git a/src/org/traccar/protocol/CalAmpProtocolDecoder.java b/src/org/traccar/protocol/CalAmpProtocolDecoder.java
index 69fca3914..99edb9fb7 100644
--- a/src/org/traccar/protocol/CalAmpProtocolDecoder.java
+++ b/src/org/traccar/protocol/CalAmpProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -63,10 +64,10 @@ public class CalAmpProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position decodePosition(int type, ChannelBuffer buf) {
+    private Position decodePosition(DeviceSession deviceSession, int type, ChannelBuffer buf) {
 
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setProtocol(getProtocolName());
 
         position.setTime(new Date(buf.readUnsignedInt() * 1000));
@@ -157,7 +158,8 @@ public class CalAmpProtocolDecoder extends BaseProtocolDecoder {
                     }
                 }
 
-                identify(String.valueOf(id), channel, remoteAddress);
+                getDeviceSession(channel, remoteAddress, String.valueOf(id));
+
             }
 
             if (BitUtil.check(content, 1)) {
@@ -182,7 +184,8 @@ public class CalAmpProtocolDecoder extends BaseProtocolDecoder {
 
         }
 
-        if (!hasDeviceId()) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -195,7 +198,7 @@ public class CalAmpProtocolDecoder extends BaseProtocolDecoder {
         }
 
         if (type == MSG_EVENT_REPORT || type == MSG_LOCATE_REPORT || type == MSG_MINI_EVENT_REPORT) {
-            return decodePosition(type, buf);
+            return decodePosition(deviceSession, type, buf);
         }
 
         return null;
diff --git a/src/org/traccar/protocol/CarTrackProtocolDecoder.java b/src/org/traccar/protocol/CarTrackProtocolDecoder.java
index ff9d32c49..e0fd60b15 100644
--- a/src/org/traccar/protocol/CarTrackProtocolDecoder.java
+++ b/src/org/traccar/protocol/CarTrackProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -67,10 +68,11 @@ public class CarTrackProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set("command", parser.next());
 
diff --git a/src/org/traccar/protocol/CarcellProtocolDecoder.java b/src/org/traccar/protocol/CarcellProtocolDecoder.java
index 50b294f45..7aacfa4d0 100644
--- a/src/org/traccar/protocol/CarcellProtocolDecoder.java
+++ b/src/org/traccar/protocol/CarcellProtocolDecoder.java
@@ -20,6 +20,7 @@ import java.util.regex.Pattern;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.Parser.CoordinateFormat;
@@ -91,11 +92,11 @@ public class CarcellProtocolDecoder extends BaseProtocolDecoder {
         position.set(Position.KEY_ARCHIVE, parser.next().equals("%"));
         position.setValid(true);
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (parser.hasNext(8)) {
             position.setLatitude(parser.nextCoordinate(CoordinateFormat.HEM_DEG_MIN_MIN));
diff --git a/src/org/traccar/protocol/CarscopProtocolDecoder.java b/src/org/traccar/protocol/CarscopProtocolDecoder.java
index 4c1aced57..5e1973ae8 100644
--- a/src/org/traccar/protocol/CarscopProtocolDecoder.java
+++ b/src/org/traccar/protocol/CarscopProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -53,12 +54,15 @@ public class CarscopProtocolDecoder extends BaseProtocolDecoder {
 
         String sentence = (String) msg;
 
+        DeviceSession deviceSession;
         int index = sentence.indexOf("UB05");
         if (index != -1) {
             String imei = sentence.substring(index + 4, index + 4 + 15);
-            identify(imei, channel, remoteAddress);
+            deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        } else {
+            deviceSession = getDeviceSession(channel, remoteAddress);
         }
-        if (!hasDeviceId()) {
+        if (deviceSession == null) {
             return null;
         }
 
@@ -68,7 +72,7 @@ public class CarscopProtocolDecoder extends BaseProtocolDecoder {
         }
 
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setProtocol(getProtocolName());
 
         DateBuilder dateBuilder = new DateBuilder()
diff --git a/src/org/traccar/protocol/CastelProtocolDecoder.java b/src/org/traccar/protocol/CastelProtocolDecoder.java
index e379b6f2d..212096018 100644
--- a/src/org/traccar/protocol/CastelProtocolDecoder.java
+++ b/src/org/traccar/protocol/CastelProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -52,11 +53,11 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
     private static final short MSG_CC_HEARTBEAT = 0x4206;
     private static final short MSG_CC_HEARTBEAT_RESPONSE = (short) 0x8206;
 
-    private Position readPosition(ChannelBuffer buf) {
+    private Position readPosition(DeviceSession deviceSession, ChannelBuffer buf) {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(buf.readUnsignedByte(), buf.readUnsignedByte(), buf.readUnsignedByte())
@@ -148,7 +149,9 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
         ChannelBuffer id = buf.readBytes(20);
         int type = ChannelBuffers.swapShort(buf.readShort());
 
-        if (!identify(id.toString(StandardCharsets.US_ASCII).trim(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(
+                channel, remoteAddress, id.toString(StandardCharsets.US_ASCII).trim());
+        if (deviceSession == null) {
             return null;
         }
 
@@ -162,7 +165,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
                 buf.readUnsignedInt(); // unix time
                 buf.readUnsignedByte();
 
-                return readPosition(buf);
+                return readPosition(deviceSession, buf);
 
             }
 
@@ -205,7 +208,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
                 List<Position> positions = new LinkedList<>();
 
                 for (int i = 0; i < count; i++) {
-                    Position position = readPosition(buf);
+                    Position position = readPosition(deviceSession, buf);
                     position.set(Position.KEY_ODOMETER, odometer);
                     position.set(Position.KEY_STATUS, status);
                     positions.add(position);
@@ -217,7 +220,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
 
             } else if (type == MSG_SC_GPS_SLEEP || type == MSG_SC_AGPS_REQUEST) {
 
-                return readPosition(buf);
+                return readPosition(deviceSession, buf);
 
             }
 
@@ -233,7 +236,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
                 List<Position> positions = new LinkedList<>();
 
                 for (int i = 0; i < count; i++) {
-                    Position position = readPosition(buf);
+                    Position position = readPosition(deviceSession, buf);
 
                     position.set(Position.KEY_STATUS, buf.readUnsignedInt());
                     position.set(Position.KEY_BATTERY, buf.readUnsignedByte());
@@ -255,7 +258,7 @@ public class CastelProtocolDecoder extends BaseProtocolDecoder {
 
                 sendResponse(channel, remoteAddress, version, id, MSG_CC_LOGIN_RESPONSE, null);
 
-                Position position = readPosition(buf);
+                Position position = readPosition(deviceSession, buf);
 
                 position.set(Position.KEY_STATUS, buf.readUnsignedInt());
                 position.set(Position.KEY_BATTERY, buf.readUnsignedByte());
diff --git a/src/org/traccar/protocol/CellocatorProtocolDecoder.java b/src/org/traccar/protocol/CellocatorProtocolDecoder.java
index f5a77e387..f074cb5d3 100644
--- a/src/org/traccar/protocol/CellocatorProtocolDecoder.java
+++ b/src/org/traccar/protocol/CellocatorProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -89,10 +90,11 @@ public class CellocatorProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            if (!identify(String.valueOf(deviceUniqueId), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(deviceUniqueId));
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             buf.readUnsignedByte(); // hardware version
             buf.readUnsignedByte(); // software version
diff --git a/src/org/traccar/protocol/CityeasyProtocolDecoder.java b/src/org/traccar/protocol/CityeasyProtocolDecoder.java
index 77d7570dc..5cdbe525d 100644
--- a/src/org/traccar/protocol/CityeasyProtocolDecoder.java
+++ b/src/org/traccar/protocol/CityeasyProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -73,8 +74,9 @@ public class CityeasyProtocolDecoder extends BaseProtocolDecoder {
         buf.readUnsignedShort(); // length
 
         String imei = ChannelBuffers.hexDump(buf.readBytes(7));
-        if (!identify(imei, channel, remoteAddress, false)
-                && !identify(imei + Checksum.luhn(Long.parseLong(imei)), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(
+                channel, remoteAddress, imei, imei + Checksum.luhn(Long.parseLong(imei)));
+        if (deviceSession == null) {
             return null;
         }
 
@@ -90,7 +92,7 @@ public class CityeasyProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             if (parser.hasNext(15)) {
 
diff --git a/src/org/traccar/protocol/DishaProtocolDecoder.java b/src/org/traccar/protocol/DishaProtocolDecoder.java
index 02f92d017..fb540c8d3 100644
--- a/src/org/traccar/protocol/DishaProtocolDecoder.java
+++ b/src/org/traccar/protocol/DishaProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -68,10 +69,11 @@ public class DishaProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.next().equals("A"));
 
diff --git a/src/org/traccar/protocol/EasyTrackProtocolDecoder.java b/src/org/traccar/protocol/EasyTrackProtocolDecoder.java
index 013b9cc43..fa792d7b5 100644
--- a/src/org/traccar/protocol/EasyTrackProtocolDecoder.java
+++ b/src/org/traccar/protocol/EasyTrackProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -70,10 +71,11 @@ public class EasyTrackProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set("command", parser.next());
 
diff --git a/src/org/traccar/protocol/EelinkProtocolDecoder.java b/src/org/traccar/protocol/EelinkProtocolDecoder.java
index e9de73dd5..85f231a17 100644
--- a/src/org/traccar/protocol/EelinkProtocolDecoder.java
+++ b/src/org/traccar/protocol/EelinkProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -63,10 +64,10 @@ public class EelinkProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position decodeOld(ChannelBuffer buf, int type, int index) {
+    private Position decodeOld(DeviceSession deviceSession, ChannelBuffer buf, int type, int index) {
 
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, index);
@@ -95,10 +96,10 @@ public class EelinkProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position decodeNew(ChannelBuffer buf, int type, int index) {
+    private Position decodeNew(DeviceSession deviceSession, ChannelBuffer buf, int type, int index) {
 
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, index);
@@ -164,13 +165,18 @@ public class EelinkProtocolDecoder extends BaseProtocolDecoder {
 
         if (type == MSG_LOGIN) {
 
-            identify(ChannelBuffers.hexDump(buf.readBytes(8)).substring(1), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, ChannelBuffers.hexDump(buf.readBytes(8)).substring(1));
+
+        } else {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
-        } else if (hasDeviceId()) {
             if (type == MSG_GPS || type == MSG_ALARM || type == MSG_STATE || type == MSG_SMS) {
-                return decodeOld(buf, type, index);
+                return decodeOld(deviceSession, buf, type, index);
             } else if (type >= MSG_NORMAL && type <= MSG_OBD_CODE) {
-                return decodeNew(buf, type, index);
+                return decodeNew(deviceSession, buf, type, index);
             }
         }
 
diff --git a/src/org/traccar/protocol/EnforaProtocolDecoder.java b/src/org/traccar/protocol/EnforaProtocolDecoder.java
index 23cfb0093..e9a32da2d 100644
--- a/src/org/traccar/protocol/EnforaProtocolDecoder.java
+++ b/src/org/traccar/protocol/EnforaProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBufferIndexFinder;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -77,7 +78,8 @@ public class EnforaProtocolDecoder extends BaseProtocolDecoder {
         }
 
         String imei = buf.toString(index, IMEI_LENGTH, StandardCharsets.US_ASCII);
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -95,7 +97,7 @@ public class EnforaProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/FlextrackProtocolDecoder.java b/src/org/traccar/protocol/FlextrackProtocolDecoder.java
index a0f151ac2..0ce2ab780 100644
--- a/src/org/traccar/protocol/FlextrackProtocolDecoder.java
+++ b/src/org/traccar/protocol/FlextrackProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -87,12 +88,15 @@ public class FlextrackProtocolDecoder extends BaseProtocolDecoder {
             String id = parser.next();
             String iccid = parser.next();
 
-            if (!identify(iccid, channel, remoteAddress, false) && !identify(id, channel, remoteAddress)) {
+            getDeviceSession(channel, remoteAddress, iccid, id);
+
+        } else if (sentence.contains("UNITSTAT")) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
                 return null;
             }
 
-        } else if (sentence.contains("UNITSTAT") && hasDeviceId()) {
-
             Parser parser = new Parser(PATTERN, sentence);
             if (!parser.matches()) {
                 return null;
@@ -100,7 +104,7 @@ public class FlextrackProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             sendAcknowledgement(channel, parser.next());
 
diff --git a/src/org/traccar/protocol/FoxProtocolDecoder.java b/src/org/traccar/protocol/FoxProtocolDecoder.java
index ac267f567..fa14e7029 100644
--- a/src/org/traccar/protocol/FoxProtocolDecoder.java
+++ b/src/org/traccar/protocol/FoxProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -78,7 +79,8 @@ public class FoxProtocolDecoder extends BaseProtocolDecoder {
 
         if (id != null && data != null) {
 
-            if (!identify(id, channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+            if (deviceSession == null) {
                 return null;
             }
 
@@ -89,7 +91,7 @@ public class FoxProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_STATUS, parser.nextInt());
 
diff --git a/src/org/traccar/protocol/FreedomProtocolDecoder.java b/src/org/traccar/protocol/FreedomProtocolDecoder.java
index 03ab894c5..3a05486eb 100644
--- a/src/org/traccar/protocol/FreedomProtocolDecoder.java
+++ b/src/org/traccar/protocol/FreedomProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -56,10 +57,11 @@ public class FreedomProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(true);
 
diff --git a/src/org/traccar/protocol/GalileoProtocolDecoder.java b/src/org/traccar/protocol/GalileoProtocolDecoder.java
index 1b03f842c..12b35333d 100644
--- a/src/org/traccar/protocol/GalileoProtocolDecoder.java
+++ b/src/org/traccar/protocol/GalileoProtocolDecoder.java
@@ -19,7 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
-import org.traccar.helper.Log;
+import org.traccar.DeviceSession;
 import org.traccar.model.Position;
 
 import java.net.SocketAddress;
@@ -146,9 +146,7 @@ public class GalileoProtocolDecoder extends BaseProtocolDecoder {
             switch (tag) {
 
                 case TAG_IMEI:
-                    String imei = buf.toString(buf.readerIndex(), 15, StandardCharsets.US_ASCII);
-                    buf.skipBytes(imei.length());
-                    identify(imei, channel, remoteAddress);
+                    getDeviceSession(channel, remoteAddress, buf.readBytes(15).toString(StandardCharsets.US_ASCII));
                     break;
 
                 case TAG_DATE:
@@ -219,8 +217,8 @@ public class GalileoProtocolDecoder extends BaseProtocolDecoder {
             positions.add(position);
         }
 
-        if (!hasDeviceId()) {
-            Log.warning("Unknown device");
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -228,7 +226,7 @@ public class GalileoProtocolDecoder extends BaseProtocolDecoder {
 
         for (Position p : positions) {
             p.setProtocol(getProtocolName());
-            p.setDeviceId(getDeviceId());
+            p.setDeviceId(deviceSession.getDeviceId());
         }
 
         if (positions.isEmpty()) {
diff --git a/src/org/traccar/protocol/GatorProtocolDecoder.java b/src/org/traccar/protocol/GatorProtocolDecoder.java
index ade27a56a..88da9a37f 100644
--- a/src/org/traccar/protocol/GatorProtocolDecoder.java
+++ b/src/org/traccar/protocol/GatorProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -90,10 +91,11 @@ public class GatorProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            if (!identify("1" + id, channel, remoteAddress, false) && !identify(id, channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, "1" + id, id);
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setYear(BcdUtil.readInteger(buf, 2))
diff --git a/src/org/traccar/protocol/Gl100ProtocolDecoder.java b/src/org/traccar/protocol/Gl100ProtocolDecoder.java
index 31102a676..d9e5bc6e6 100644
--- a/src/org/traccar/protocol/Gl100ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gl100ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -75,10 +76,11 @@ public class Gl100ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.nextInt() == 0);
         position.setSpeed(parser.nextDouble());
diff --git a/src/org/traccar/protocol/Gl200ProtocolDecoder.java b/src/org/traccar/protocol/Gl200ProtocolDecoder.java
index 2793e123a..670b9fa96 100644
--- a/src/org/traccar/protocol/Gl200ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gl200ProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -258,10 +259,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_STATUS, parser.next());
         position.set(Position.KEY_POWER, parser.next());
@@ -318,10 +320,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_RPM, parser.next());
         position.set(Position.KEY_OBD_SPEED, parser.next());
@@ -359,7 +362,8 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
 
         LinkedList<Position> positions = new LinkedList<>();
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
 
@@ -370,7 +374,7 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         while (itemParser.find()) {
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_VIN, vin);
 
@@ -433,10 +437,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         decodeLocation(position, parser);
 
@@ -464,10 +469,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_RFID, parser.next());
 
@@ -496,10 +502,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int reportType = parser.nextInt();
         if (type.equals("NMR")) {
@@ -539,10 +546,11 @@ public class Gl200ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setSpeed(UnitsConverter.knotsFromKph(parser.nextDouble()));
         position.setCourse(parser.nextDouble());
diff --git a/src/org/traccar/protocol/GlobalSatProtocolDecoder.java b/src/org/traccar/protocol/GlobalSatProtocolDecoder.java
index b8bb742e4..084279732 100644
--- a/src/org/traccar/protocol/GlobalSatProtocolDecoder.java
+++ b/src/org/traccar/protocol/GlobalSatProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -84,10 +85,11 @@ public class GlobalSatProtocolDecoder extends BaseProtocolDecoder {
 
             switch (format.charAt(formatIndex)) {
                 case 'S':
-                    if (!identify(value, channel, remoteAddress)) {
+                    DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, value);
+                    if (deviceSession == null) {
                         return null;
                     }
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
                     break;
                 case 'A':
                     if (value.isEmpty()) {
@@ -203,10 +205,11 @@ public class GlobalSatProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(!parser.next().equals("1"));
 
diff --git a/src/org/traccar/protocol/GnxProtocolDecoder.java b/src/org/traccar/protocol/GnxProtocolDecoder.java
index 3b1cccfc4..a2ee5ae48 100644
--- a/src/org/traccar/protocol/GnxProtocolDecoder.java
+++ b/src/org/traccar/protocol/GnxProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -87,10 +88,11 @@ public class GnxProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (parser.nextInt() == 1) {
             position.set(Position.KEY_ARCHIVE, true);
diff --git a/src/org/traccar/protocol/GoSafeProtocolDecoder.java b/src/org/traccar/protocol/GoSafeProtocolDecoder.java
index 50e39d67f..8ce53cc40 100644
--- a/src/org/traccar/protocol/GoSafeProtocolDecoder.java
+++ b/src/org/traccar/protocol/GoSafeProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -126,11 +127,11 @@ public class GoSafeProtocolDecoder extends BaseProtocolDecoder {
             .any()
             .compile();
 
-    private Position decodePosition(Parser parser, Date time) {
+    private Position decodePosition(DeviceSession deviceSession, Parser parser, Date time) {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (time != null) {
             position.setTime(time);
@@ -192,7 +193,8 @@ public class GoSafeProtocolDecoder extends BaseProtocolDecoder {
             return null;
         }
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
 
@@ -200,7 +202,7 @@ public class GoSafeProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt());
@@ -231,7 +233,7 @@ public class GoSafeProtocolDecoder extends BaseProtocolDecoder {
             List<Position> positions = new LinkedList<>();
             Parser itemParser = new Parser(PATTERN_ITEM, parser.next());
             while (itemParser.find()) {
-                positions.add(decodePosition(itemParser, time));
+                positions.add(decodePosition(deviceSession, itemParser, time));
             }
 
             return positions;
diff --git a/src/org/traccar/protocol/GotopProtocolDecoder.java b/src/org/traccar/protocol/GotopProtocolDecoder.java
index a62cfc623..0dcae3c8d 100644
--- a/src/org/traccar/protocol/GotopProtocolDecoder.java
+++ b/src/org/traccar/protocol/GotopProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -58,10 +59,11 @@ public class GotopProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.next().equals("A"));
 
diff --git a/src/org/traccar/protocol/Gps103ProtocolDecoder.java b/src/org/traccar/protocol/Gps103ProtocolDecoder.java
index f8256a5ab..821cf2d21 100644
--- a/src/org/traccar/protocol/Gps103ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gps103ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -113,7 +114,7 @@ public class Gps103ProtocolDecoder extends BaseProtocolDecoder {
                 channel.write("LOAD", remoteAddress);
                 Parser handshakeParser = new Parser(PATTERN_HANDSHAKE, sentence);
                 if (handshakeParser.matches()) {
-                    identify(handshakeParser.next(), channel, remoteAddress);
+                    getDeviceSession(channel, remoteAddress, handshakeParser.next());
                 }
             }
             return null;
@@ -138,10 +139,11 @@ public class Gps103ProtocolDecoder extends BaseProtocolDecoder {
         Parser parser = new Parser(PATTERN_NETWORK, sentence);
         if (parser.matches()) {
 
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             getLastLocation(position, null);
 
@@ -155,10 +157,11 @@ public class Gps103ProtocolDecoder extends BaseProtocolDecoder {
         parser = new Parser(PATTERN_OBD, sentence);
         if (parser.matches()) {
 
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
@@ -185,10 +188,11 @@ public class Gps103ProtocolDecoder extends BaseProtocolDecoder {
         }
 
         String imei = parser.next();
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         String alarm = parser.next();
         position.set(Position.KEY_ALARM, alarm);
diff --git a/src/org/traccar/protocol/GpsGateProtocolDecoder.java b/src/org/traccar/protocol/GpsGateProtocolDecoder.java
index 127c986a3..1cb0ddfde 100644
--- a/src/org/traccar/protocol/GpsGateProtocolDecoder.java
+++ b/src/org/traccar/protocol/GpsGateProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -85,7 +86,8 @@ public class GpsGateProtocolDecoder extends BaseProtocolDecoder {
                 int endIndex = sentence.indexOf(',', beginIndex);
                 if (endIndex != -1) {
                     String imei = sentence.substring(beginIndex, endIndex);
-                    if (identify(imei, channel, remoteAddress)) {
+                    DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+                    if (deviceSession != null) {
                         if (channel != null) {
                             send(channel, "$FRSES," + channel.getId());
                         }
@@ -106,14 +108,19 @@ public class GpsGateProtocolDecoder extends BaseProtocolDecoder {
 
         } else if (sentence.startsWith("$GPRMC,")) {
 
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
+
             Parser parser = new Parser(PATTERN_GPRMC, sentence);
-            if (!parser.matches() || !hasDeviceId()) {
+            if (!parser.matches()) {
                 return null;
             }
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt(), parser.nextInt());
@@ -139,10 +146,11 @@ public class GpsGateProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.setLatitude(parser.nextCoordinate());
             position.setLongitude(parser.nextCoordinate());
diff --git a/src/org/traccar/protocol/GpsMarkerProtocolDecoder.java b/src/org/traccar/protocol/GpsMarkerProtocolDecoder.java
index 515958339..4f6faa6ba 100644
--- a/src/org/traccar/protocol/GpsMarkerProtocolDecoder.java
+++ b/src/org/traccar/protocol/GpsMarkerProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -64,10 +65,11 @@ public class GpsMarkerProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/GpsmtaProtocolDecoder.java b/src/org/traccar/protocol/GpsmtaProtocolDecoder.java
index b46d4c6f2..f10b3771c 100644
--- a/src/org/traccar/protocol/GpsmtaProtocolDecoder.java
+++ b/src/org/traccar/protocol/GpsmtaProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
 import org.traccar.model.Position;
@@ -59,10 +60,11 @@ public class GpsmtaProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         String time = parser.next();
         position.setTime(new Date(Long.parseLong(time) * 1000));
diff --git a/src/org/traccar/protocol/GranitProtocolDecoder.java b/src/org/traccar/protocol/GranitProtocolDecoder.java
index 7432961b0..0c7ea4d1d 100644
--- a/src/org/traccar/protocol/GranitProtocolDecoder.java
+++ b/src/org/traccar/protocol/GranitProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.StringFinder;
@@ -136,11 +137,13 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
 
         int indexTilde = buf.indexOf(buf.readerIndex(), buf.writerIndex(), new StringFinder("~"));
 
-        if (hasDeviceId() && indexTilde == -1) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+
+        if (deviceSession != null && indexTilde == -1) {
             String bufString = buf.toString(StandardCharsets.US_ASCII);
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.setTime(new Date());
             getLastLocation(position, new Date());
@@ -155,9 +158,11 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
         String header = buf.readBytes(HEADER_LENGTH).toString(StandardCharsets.US_ASCII);
 
         if (header.equals("+RRCB~")) {
+
             buf.skipBytes(2); //binary length 26
             int deviceId = buf.readUnsignedShort();
-            if (!identify(String.valueOf(deviceId), channel, remoteAddress)) {
+            deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(deviceId));
+            if (deviceSession == null) {
                 return null;
             }
             long unixTime = buf.readUnsignedInt();
@@ -166,7 +171,7 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
             }
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.setTime(new Date(unixTime * 1000));
 
@@ -174,9 +179,11 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
             return position;
 
         } else if (header.equals("+DDAT~")) {
+
             buf.skipBytes(2); //binary length
             int deviceId = buf.readUnsignedShort();
-            if (!identify(String.valueOf(deviceId), channel, remoteAddress)) {
+            deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(deviceId));
+            if (deviceSession == null) {
                 return null;
             }
             byte format = buf.readByte();
@@ -197,7 +204,7 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
                     if (buf.getUnsignedByte(buf.readerIndex()) != 0xFE) {
                         Position position = new Position();
                         position.setProtocol(getProtocolName());
-                        position.setDeviceId(getDeviceId());
+                        position.setDeviceId(deviceSession.getDeviceId());
                         position.setTime(new Date((unixTime + i * timeIncrement) * 1000));
                         decodeStructure(buf, position);
                         positions.add(position);
@@ -208,7 +215,10 @@ public class GranitProtocolDecoder extends BaseProtocolDecoder {
                 buf.skipBytes(2); // increment
             }
             return positions;
+
         }
+
         return null;
     }
+
 }
diff --git a/src/org/traccar/protocol/Gt02ProtocolDecoder.java b/src/org/traccar/protocol/Gt02ProtocolDecoder.java
index 2cc31bb30..d93b93b83 100644
--- a/src/org/traccar/protocol/Gt02ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gt02ProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -52,10 +53,11 @@ public class Gt02ProtocolDecoder extends BaseProtocolDecoder {
         int gsm = buf.readUnsignedByte();
 
         String imei = ChannelBuffers.hexDump(buf.readBytes(8)).substring(1);
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_INDEX, buf.readUnsignedShort());
 
diff --git a/src/org/traccar/protocol/Gt06ProtocolDecoder.java b/src/org/traccar/protocol/Gt06ProtocolDecoder.java
index 57e2d64b7..f89d20fce 100644
--- a/src/org/traccar/protocol/Gt06ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Gt06ProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
@@ -175,7 +176,6 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
 
             int length = buf.readUnsignedByte();
             int dataLength = length - 5;
-
             int type = buf.readUnsignedByte();
 
             if (type == MSG_LOGIN) {
@@ -197,17 +197,23 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
                     }
                 }
 
-                if (identify(imei, channel, remoteAddress)) {
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+                if (deviceSession != null) {
                     buf.skipBytes(buf.readableBytes() - 6);
                     sendResponse(channel, type, buf.readUnsignedShort());
                 }
 
-            } else if (hasDeviceId()) {
+            } else {
+
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+                if (deviceSession == null) {
+                    return null;
+                }
 
                 if (type == MSG_STRING) {
 
                     Position position = new Position();
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
                     position.setProtocol(getProtocolName());
 
                     getLastLocation(position, null);
@@ -228,7 +234,7 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
                 } else if (isSupported(type)) {
 
                     Position position = new Position();
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
                     position.setProtocol(getProtocolName());
 
                     if (hasGps(type)) {
@@ -271,39 +277,31 @@ public class Gt06ProtocolDecoder extends BaseProtocolDecoder {
 
         } else if (header == 0x7979) {
 
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
+
             buf.readUnsignedShort(); // length
             int type = buf.readUnsignedByte();
 
             if (type == MSG_INFO) {
                 int subType = buf.readUnsignedByte();
 
-                if (subType == 0x00) {
+                Position position = new Position();
+                position.setDeviceId(deviceSession.getDeviceId());
+                position.setProtocol(getProtocolName());
 
-                    Position position = new Position();
-                    position.setDeviceId(getDeviceId());
-                    position.setProtocol(getProtocolName());
-
-                    getLastLocation(position, null);
+                getLastLocation(position, null);
 
+                if (subType == 0x00) {
                     position.set(Position.KEY_POWER, buf.readUnsignedShort() * 0.01);
-
                     return position;
-
                 } else if (subType == 0x05) {
-
-                    Position position = new Position();
-                    position.setDeviceId(getDeviceId());
-                    position.setProtocol(getProtocolName());
-
-                    getLastLocation(position, null);
-
                     int flags = buf.readUnsignedByte();
-
                     position.set("door", BitUtil.check(flags, 0));
                     position.set(Position.PREFIX_IO + 1, BitUtil.check(flags, 2));
-
                     return position;
-
                 }
             }
 
diff --git a/src/org/traccar/protocol/H02ProtocolDecoder.java b/src/org/traccar/protocol/H02ProtocolDecoder.java
index ec5d3adef..b340973e6 100644
--- a/src/org/traccar/protocol/H02ProtocolDecoder.java
+++ b/src/org/traccar/protocol/H02ProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
@@ -78,10 +79,12 @@ public class H02ProtocolDecoder extends BaseProtocolDecoder {
 
         buf.readByte(); // marker
 
-        if (!identify(ChannelBuffers.hexDump(buf.readBytes(5)), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(
+                channel, remoteAddress, ChannelBuffers.hexDump(buf.readBytes(5)));
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setHour(BcdUtil.readInteger(buf, 2))
@@ -152,10 +155,11 @@ public class H02ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder();
         if (parser.hasNext(3)) {
diff --git a/src/org/traccar/protocol/HaicomProtocolDecoder.java b/src/org/traccar/protocol/HaicomProtocolDecoder.java
index f8509d63a..647477d50 100644
--- a/src/org/traccar/protocol/HaicomProtocolDecoder.java
+++ b/src/org/traccar/protocol/HaicomProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -65,10 +66,11 @@ public class HaicomProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_VERSION, parser.next());
 
diff --git a/src/org/traccar/protocol/HomtecsProtocolDecoder.java b/src/org/traccar/protocol/HomtecsProtocolDecoder.java
index c09ef75b1..21eb2c0b5 100644
--- a/src/org/traccar/protocol/HomtecsProtocolDecoder.java
+++ b/src/org/traccar/protocol/HomtecsProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -57,10 +58,11 @@ public class HomtecsProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/HuaShengProtocolDecoder.java b/src/org/traccar/protocol/HuaShengProtocolDecoder.java
index 50517045b..6901f37fb 100644
--- a/src/org/traccar/protocol/HuaShengProtocolDecoder.java
+++ b/src/org/traccar/protocol/HuaShengProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -75,7 +76,8 @@ public class HuaShengProtocolDecoder extends BaseProtocolDecoder {
                 int length = buf.readUnsignedShort() - 4;
                 if (subtype == 0x0003) {
                     String imei = buf.readBytes(length).toString(StandardCharsets.US_ASCII);
-                    if (identify(imei, channel, remoteAddress) && channel != null) {
+                    DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+                    if (deviceSession != null && channel != null) {
                         ChannelBuffer content = ChannelBuffers.dynamicBuffer();
                         content.writeByte(0); // success
                         sendResponse(channel, MSG_LOGIN_RSP, content);
@@ -87,9 +89,14 @@ public class HuaShengProtocolDecoder extends BaseProtocolDecoder {
 
         } else if (type == MSG_POSITION) {
 
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
+
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_STATUS, buf.readUnsignedShort());
             position.set(Position.KEY_EVENT, buf.readUnsignedShort());
diff --git a/src/org/traccar/protocol/HuabaoProtocolDecoder.java b/src/org/traccar/protocol/HuabaoProtocolDecoder.java
index 55473e180..e4c9a9860 100644
--- a/src/org/traccar/protocol/HuabaoProtocolDecoder.java
+++ b/src/org/traccar/protocol/HuabaoProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.Checksum;
@@ -81,7 +82,8 @@ public class HuabaoProtocolDecoder extends BaseProtocolDecoder {
         ChannelBuffer id = buf.readBytes(6); // phone number
         int index = buf.readUnsignedShort();
 
-        if (!identify(ChannelBuffers.hexDump(id), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, ChannelBuffers.hexDump(id));
+        if (deviceSession == null) {
             return null;
         }
 
@@ -101,7 +103,7 @@ public class HuabaoProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_ALARM, buf.readUnsignedInt());
 
diff --git a/src/org/traccar/protocol/IdplProtocolDecoder.java b/src/org/traccar/protocol/IdplProtocolDecoder.java
index 322a1e9fb..b0d331e3e 100644
--- a/src/org/traccar/protocol/IdplProtocolDecoder.java
+++ b/src/org/traccar/protocol/IdplProtocolDecoder.java
@@ -20,6 +20,7 @@ import java.util.regex.Pattern;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.Protocol;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -74,10 +75,11 @@ public class IdplProtocolDecoder extends BaseProtocolDecoder {
 
         position.set(Position.KEY_TYPE, parser.nextInt());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/IntellitracProtocolDecoder.java b/src/org/traccar/protocol/IntellitracProtocolDecoder.java
index 98ba90aa7..06d6476e6 100644
--- a/src/org/traccar/protocol/IntellitracProtocolDecoder.java
+++ b/src/org/traccar/protocol/IntellitracProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -75,10 +76,11 @@ public class IntellitracProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/Jt600ProtocolDecoder.java b/src/org/traccar/protocol/Jt600ProtocolDecoder.java
index 6529ff124..7e0b54456 100644
--- a/src/org/traccar/protocol/Jt600ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Jt600ProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -50,10 +51,11 @@ public class Jt600ProtocolDecoder extends BaseProtocolDecoder {
         buf.readByte(); // header
 
         String id = String.valueOf(Long.parseLong(ChannelBuffers.hexDump(buf.readBytes(5))));
-        if (!identify(id, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int version = BcdUtil.readInteger(buf, 1);
         buf.readUnsignedByte(); // type
@@ -151,10 +153,11 @@ public class Jt600ProtocolDecoder extends BaseProtocolDecoder {
 
         position.set(Position.KEY_ALARM, true);
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setLongitude(parser.nextCoordinate());
         position.setLatitude(parser.nextCoordinate());
diff --git a/src/org/traccar/protocol/KenjiProtocolDecoder.java b/src/org/traccar/protocol/KenjiProtocolDecoder.java
index 2756cb1ec..2a95717ee 100755
--- a/src/org/traccar/protocol/KenjiProtocolDecoder.java
+++ b/src/org/traccar/protocol/KenjiProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -60,10 +61,11 @@ public class KenjiProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_ALARM, parser.nextInt(16));
         position.set(Position.KEY_OUTPUT, parser.nextInt(16));
diff --git a/src/org/traccar/protocol/KhdProtocolDecoder.java b/src/org/traccar/protocol/KhdProtocolDecoder.java
index f4350d2cc..e34a24b40 100644
--- a/src/org/traccar/protocol/KhdProtocolDecoder.java
+++ b/src/org/traccar/protocol/KhdProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
@@ -73,10 +74,11 @@ public class KhdProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            if (!identify(readSerialNumber(buf), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, readSerialNumber(buf));
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setYear(BcdUtil.readInteger(buf, 2))
diff --git a/src/org/traccar/protocol/LaipacProtocolDecoder.java b/src/org/traccar/protocol/LaipacProtocolDecoder.java
index ba0dad4b4..ebca443a1 100644
--- a/src/org/traccar/protocol/LaipacProtocolDecoder.java
+++ b/src/org/traccar/protocol/LaipacProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -68,10 +69,11 @@ public class LaipacProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/M2mProtocolDecoder.java b/src/org/traccar/protocol/M2mProtocolDecoder.java
index 9a328472c..601b6d191 100644
--- a/src/org/traccar/protocol/M2mProtocolDecoder.java
+++ b/src/org/traccar/protocol/M2mProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
 
@@ -58,13 +59,18 @@ public class M2mProtocolDecoder extends BaseProtocolDecoder {
                 imei.append(b % 10);
             }
 
-            identify(imei.toString(), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, imei.toString());
 
-        } else if (hasDeviceId()) {
+        } else {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDay(buf.readUnsignedByte() & 0x3f)
diff --git a/src/org/traccar/protocol/ManPowerProtocolDecoder.java b/src/org/traccar/protocol/ManPowerProtocolDecoder.java
index 5ff111927..a2ede32b8 100644
--- a/src/org/traccar/protocol/ManPowerProtocolDecoder.java
+++ b/src/org/traccar/protocol/ManPowerProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -60,10 +61,11 @@ public class ManPowerProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_STATUS, parser.next());
 
diff --git a/src/org/traccar/protocol/MegastekProtocolDecoder.java b/src/org/traccar/protocol/MegastekProtocolDecoder.java
index ca554aa48..1ff7add1a 100644
--- a/src/org/traccar/protocol/MegastekProtocolDecoder.java
+++ b/src/org/traccar/protocol/MegastekProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -157,10 +158,11 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
 
                 position.set(Position.KEY_ALARM, parser.next());
 
-                if (!identify(parser.next(), channel, remoteAddress, false) && !identify(id, channel, remoteAddress)) {
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next(), id);
+                if (deviceSession == null) {
                     return null;
                 }
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 position.set(Position.KEY_SATELLITES, parser.next());
 
@@ -182,10 +184,11 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
 
             } else {
 
-                if (!identify(id, channel, remoteAddress)) {
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+                if (deviceSession == null) {
                     return null;
                 }
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
             }
 
@@ -194,10 +197,11 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
             Parser parser = new Parser(PATTERN_ALTERNATIVE, status);
             if (parser.matches()) {
 
-                if (!identify(id, channel, remoteAddress)) {
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+                if (deviceSession == null) {
                     return null;
                 }
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 position.set(Position.KEY_MCC, parser.nextInt());
                 position.set(Position.KEY_MNC, parser.nextInt());
@@ -275,10 +279,11 @@ public class MegastekProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (parser.next().equals("S")) {
             position.set(Position.KEY_ARCHIVE, true);
diff --git a/src/org/traccar/protocol/MeiligaoProtocolDecoder.java b/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
index cdbf3850a..9c7e9ea23 100644
--- a/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
+++ b/src/org/traccar/protocol/MeiligaoProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -90,7 +91,7 @@ public class MeiligaoProtocolDecoder extends BaseProtocolDecoder {
 
     public static final int MSG_RFID = 0x9966;
 
-    private boolean identify(ChannelBuffer buf, Channel channel, SocketAddress remoteAddress) {
+    private DeviceSession identify(ChannelBuffer buf, Channel channel, SocketAddress remoteAddress) {
         StringBuilder builder = new StringBuilder();
 
         for (int i = 0; i < 7; i++) {
@@ -113,13 +114,11 @@ public class MeiligaoProtocolDecoder extends BaseProtocolDecoder {
 
         String id = builder.toString();
 
-        // Try to recreate full IMEI number
-        // Sometimes first digit is cut, so this won't work
-        if (id.length() == 14 && identify(id + Checksum.luhn(Long.parseLong(id)), channel, remoteAddress, false)) {
-            return true;
+        if (id.length() == 14) {
+            return getDeviceSession(channel, remoteAddress, id, id + Checksum.luhn(Long.parseLong(id)));
+        } else {
+            return getDeviceSession(channel, remoteAddress, id);
         }
-
-        return identify(id, channel, remoteAddress);
     }
 
     private static void sendResponse(
@@ -202,10 +201,11 @@ public class MeiligaoProtocolDecoder extends BaseProtocolDecoder {
             buf.skipBytes(6);
         }
 
-        if (!identify(id, channel, remoteAddress)) {
+        DeviceSession deviceSession = identify(id, channel, remoteAddress);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (command == MSG_RFID) {
             for (int i = 0; i < 15; i++) {
diff --git a/src/org/traccar/protocol/MeitrackProtocolDecoder.java b/src/org/traccar/protocol/MeitrackProtocolDecoder.java
index a7fca89fc..81b6b8f76 100644
--- a/src/org/traccar/protocol/MeitrackProtocolDecoder.java
+++ b/src/org/traccar/protocol/MeitrackProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -92,10 +93,11 @@ public class MeitrackProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int event = parser.nextInt();
         position.set(Position.KEY_EVENT, event);
@@ -173,7 +175,8 @@ public class MeitrackProtocolDecoder extends BaseProtocolDecoder {
         int index = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) ',');
 
         String imei = buf.toString(index + 1, 15, StandardCharsets.US_ASCII);
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -183,7 +186,7 @@ public class MeitrackProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_EVENT, buf.readUnsignedByte());
 
@@ -251,7 +254,8 @@ public class MeitrackProtocolDecoder extends BaseProtocolDecoder {
         switch (type) {
             case "D03":
                 if (channel != null) {
-                    String imei = Context.getIdentityManager().getDeviceById(getDeviceId()).getUniqueId();
+                    DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+                    String imei = Context.getIdentityManager().getDeviceById(deviceSession.getDeviceId()).getUniqueId();
                     channel.write("@@O46," + imei + ",D00,camera_picture.jpg,0*00\r\n");
                 }
                 return null;
diff --git a/src/org/traccar/protocol/MiniFinderProtocolDecoder.java b/src/org/traccar/protocol/MiniFinderProtocolDecoder.java
index 96eaaf0fa..3eb559cc4 100644
--- a/src/org/traccar/protocol/MiniFinderProtocolDecoder.java
+++ b/src/org/traccar/protocol/MiniFinderProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -60,9 +61,14 @@ public class MiniFinderProtocolDecoder extends BaseProtocolDecoder {
 
         if (sentence.startsWith("!1")) {
 
-            identify(sentence.substring(3, sentence.length()), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(3, sentence.length()));
 
-        } else if (sentence.matches("![A-D].*") && hasDeviceId()) {
+        } else if (sentence.matches("![A-D].*")) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Parser parser = new Parser(PATTERN, sentence);
             if (!parser.matches()) {
@@ -71,7 +77,7 @@ public class MiniFinderProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/Mta6ProtocolDecoder.java b/src/org/traccar/protocol/Mta6ProtocolDecoder.java
index 791a1acab..609f0b63e 100644
--- a/src/org/traccar/protocol/Mta6ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Mta6ProtocolDecoder.java
@@ -24,6 +24,7 @@ import org.jboss.netty.handler.codec.http.HttpResponse;
 import org.jboss.netty.handler.codec.http.HttpResponseStatus;
 import org.jboss.netty.handler.codec.http.HttpVersion;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.Protocol;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
@@ -110,7 +111,7 @@ public class Mta6ProtocolDecoder extends BaseProtocolDecoder {
 
     }
 
-    private List<Position> parseFormatA(ChannelBuffer buf) {
+    private List<Position> parseFormatA(DeviceSession deviceSession, ChannelBuffer buf) {
         List<Position> positions = new LinkedList<>();
 
         FloatReader latitudeReader = new FloatReader();
@@ -120,8 +121,8 @@ public class Mta6ProtocolDecoder extends BaseProtocolDecoder {
         try {
             while (buf.readable()) {
                 Position position = new Position();
-                position.setDeviceId(getDeviceId());
                 position.setProtocol(getProtocolName());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 short flags = buf.readUnsignedByte();
 
@@ -197,9 +198,9 @@ public class Mta6ProtocolDecoder extends BaseProtocolDecoder {
         return positions;
     }
 
-    private Position parseFormatA1(ChannelBuffer buf) {
+    private Position parseFormatA1(DeviceSession deviceSession, ChannelBuffer buf) {
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setProtocol(getProtocolName());
 
         short flags = buf.readUnsignedByte();
@@ -283,7 +284,8 @@ public class Mta6ProtocolDecoder extends BaseProtocolDecoder {
         buf.skipBytes("id=".length());
         int index = buf.indexOf(buf.readerIndex(), buf.writerIndex(), (byte) '&');
         String uniqueId = buf.toString(buf.readerIndex(), index - buf.readerIndex(), StandardCharsets.US_ASCII);
-        if (!identify(uniqueId, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, uniqueId);
+        if (deviceSession == null) {
             return null;
         }
         buf.skipBytes(uniqueId.length());
@@ -303,9 +305,9 @@ public class Mta6ProtocolDecoder extends BaseProtocolDecoder {
 
         if (packetId == 0x31 || packetId == 0x32 || packetId == 0x36) {
             if (simple) {
-                return parseFormatA1(buf);
+                return parseFormatA1(deviceSession, buf);
             } else {
-                return parseFormatA(buf);
+                return parseFormatA(deviceSession, buf);
             }
         } //else if (0x34 0x38 0x4F 0x59)
 
diff --git a/src/org/traccar/protocol/MtxProtocolDecoder.java b/src/org/traccar/protocol/MtxProtocolDecoder.java
index 8af10c7d8..e39c73d17 100644
--- a/src/org/traccar/protocol/MtxProtocolDecoder.java
+++ b/src/org/traccar/protocol/MtxProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -71,10 +72,11 @@ public class MtxProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/MxtProtocolDecoder.java b/src/org/traccar/protocol/MxtProtocolDecoder.java
index 92e941e6d..56024057e 100644
--- a/src/org/traccar/protocol/MxtProtocolDecoder.java
+++ b/src/org/traccar/protocol/MxtProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -46,7 +47,8 @@ public class MxtProtocolDecoder extends BaseProtocolDecoder {
         int type = buf.readUnsignedByte();
 
         String id = String.valueOf(buf.readUnsignedInt());
-        if (!identify(id, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -54,7 +56,7 @@ public class MxtProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             buf.readUnsignedByte(); // protocol
             int infoGroups = buf.readUnsignedByte();
diff --git a/src/org/traccar/protocol/NavigilProtocolDecoder.java b/src/org/traccar/protocol/NavigilProtocolDecoder.java
index 8dd4e140b..e2afdf8d3 100644
--- a/src/org/traccar/protocol/NavigilProtocolDecoder.java
+++ b/src/org/traccar/protocol/NavigilProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.Checksum;
 import org.traccar.helper.Log;
 import org.traccar.helper.UnitsConverter;
@@ -78,13 +79,14 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position parseUnitReport(ChannelBuffer buf, int sequenceNumber) {
+    private Position parseUnitReport(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.setValid(true);
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         buf.readUnsignedShort(); // report trigger
         buf.readUnsignedShort(); // flags
@@ -112,13 +114,14 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position parseTg2Report(ChannelBuffer buf, int sequenceNumber) {
+    private Position parseTg2Report(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.setValid(true);
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         buf.readUnsignedShort(); // report trigger
         buf.readUnsignedByte(); // reserved
@@ -148,12 +151,13 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position parsePositionReport(ChannelBuffer buf, int sequenceNumber, long timestamp) {
+    private Position parsePositionReport(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber, long timestamp) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setTime(convertTimestamp(timestamp));
 
         position.setLatitude(buf.readMedium() * 0.00002);
@@ -169,12 +173,13 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position parsePositionReport2(ChannelBuffer buf, int sequenceNumber, long timestamp) {
+    private Position parsePositionReport2(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber, long timestamp) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setTime(convertTimestamp(timestamp));
 
         position.setLatitude(buf.readInt() * 0.0000001);
@@ -192,12 +197,13 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position parseSnapshot4(ChannelBuffer buf, int sequenceNumber) {
+    private Position parseSnapshot4(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         buf.readUnsignedByte(); // report trigger
         buf.readUnsignedByte(); // position fix source
@@ -230,12 +236,13 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position parseTrackingData(ChannelBuffer buf, int sequenceNumber, long timestamp) {
+    private Position parseTrackingData(
+            DeviceSession deviceSession, ChannelBuffer buf, int sequenceNumber, long timestamp) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
         position.set(Position.KEY_INDEX, sequenceNumber);
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
         position.setTime(convertTimestamp(timestamp));
 
         buf.readUnsignedByte(); // tracking mode
@@ -273,32 +280,30 @@ public class NavigilProtocolDecoder extends BaseProtocolDecoder {
         int flags = buf.readUnsignedShort();
         buf.readUnsignedShort(); // checksum
 
-        // Get device identifier
-        if (!identify(String.valueOf(buf.readUnsignedInt()), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(buf.readUnsignedInt()));
+        if (deviceSession == null) {
             return null;
         }
 
-        long timestamp = buf.readUnsignedInt(); // message timestamp
+        long timestamp = buf.readUnsignedInt();
 
-        // Acknowledgment
         if ((flags & 0x1) == 0x0) {
             sendAcknowledgment(channel, sequenceNumber);
         }
 
-        // Parse messages
         switch (messageId) {
             case MSG_UNIT_REPORT:
-                return parseUnitReport(buf, sequenceNumber);
+                return parseUnitReport(deviceSession, buf, sequenceNumber);
             case MSG_TG2_REPORT:
-                return parseTg2Report(buf, sequenceNumber);
+                return parseTg2Report(deviceSession, buf, sequenceNumber);
             case MSG_POSITION_REPORT:
-                return parsePositionReport(buf, sequenceNumber, timestamp);
+                return parsePositionReport(deviceSession, buf, sequenceNumber, timestamp);
             case MSG_POSITION_REPORT_2:
-                return parsePositionReport2(buf, sequenceNumber, timestamp);
+                return parsePositionReport2(deviceSession, buf, sequenceNumber, timestamp);
             case MSG_SNAPSHOT4:
-                return parseSnapshot4(buf, sequenceNumber);
+                return parseSnapshot4(deviceSession, buf, sequenceNumber);
             case MSG_TRACKING_DATA:
-                return parseTrackingData(buf, sequenceNumber, timestamp);
+                return parseTrackingData(deviceSession, buf, sequenceNumber, timestamp);
             default:
                 Log.warning(new UnsupportedOperationException(String.valueOf(messageId)));
                 break;
diff --git a/src/org/traccar/protocol/NavisProtocolDecoder.java b/src/org/traccar/protocol/NavisProtocolDecoder.java
index fbd704355..fad24301c 100644
--- a/src/org/traccar/protocol/NavisProtocolDecoder.java
+++ b/src/org/traccar/protocol/NavisProtocolDecoder.java
@@ -19,9 +19,9 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
-import org.traccar.helper.Log;
 import org.traccar.model.Position;
 
 import java.net.SocketAddress;
@@ -39,7 +39,6 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
         super(protocol);
     }
 
-    // Format types
     public static final int F10 = 0x01;
     public static final int F20 = 0x02;
     public static final int F30 = 0x03;
@@ -75,11 +74,11 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private ParseResult parsePosition(ChannelBuffer buf) {
+    private ParseResult parsePosition(DeviceSession deviceSession, ChannelBuffer buf) {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int format;
         if (buf.getUnsignedByte(buf.readerIndex()) == 0) {
@@ -177,8 +176,8 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
         return new ParseResult(index, position);
     }
 
-    private Object processSingle(Channel channel, ChannelBuffer buf) {
-        ParseResult result = parsePosition(buf);
+    private Object processSingle(DeviceSession deviceSession, Channel channel, ChannelBuffer buf) {
+        ParseResult result = parsePosition(deviceSession, buf);
 
         ChannelBuffer response = ChannelBuffers.dynamicBuffer(ByteOrder.LITTLE_ENDIAN, 8);
         response.writeBytes(ChannelBuffers.copiedBuffer(ByteOrder.LITTLE_ENDIAN, "*<T", StandardCharsets.US_ASCII));
@@ -192,12 +191,12 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
         return result.getPosition();
     }
 
-    private Object processArray(Channel channel, ChannelBuffer buf) {
+    private Object processArray(DeviceSession deviceSession, Channel channel, ChannelBuffer buf) {
         List<Position> positions = new LinkedList<>();
         int count = buf.readUnsignedByte();
 
         for (int i = 0; i < count; i++) {
-            Position position = parsePosition(buf).getPosition();
+            Position position = parsePosition(deviceSession, buf).getPosition();
             if (position.getFixTime() != null) {
                 positions.add(position);
             }
@@ -217,7 +216,7 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
 
     private Object processHandshake(Channel channel, SocketAddress remoteAddress, ChannelBuffer buf) {
         buf.readByte(); // semicolon symbol
-        if (identify(buf.toString(StandardCharsets.US_ASCII), channel, remoteAddress)) {
+        if (getDeviceSession(channel, remoteAddress, buf.toString(StandardCharsets.US_ASCII)) != null) {
             sendReply(channel, ChannelBuffers.copiedBuffer(ByteOrder.LITTLE_ENDIAN, "*<S", StandardCharsets.US_ASCII));
         }
         return null;
@@ -265,16 +264,17 @@ public class NavisProtocolDecoder extends BaseProtocolDecoder {
         String type = buf.toString(buf.readerIndex(), 3, StandardCharsets.US_ASCII);
         buf.skipBytes(type.length());
 
-        switch (type) {
-            case "*>T":
-                return processSingle(channel, buf);
-            case "*>A":
-                return processArray(channel, buf);
-            case "*>S":
-                return processHandshake(channel, remoteAddress, buf);
-            default:
-                Log.warning(new UnsupportedOperationException(type));
-                break;
+        if (type.equals("*>S")) {
+            return processHandshake(channel, remoteAddress, buf);
+        } else {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession != null) {
+                if (type.equals("*>T")) {
+                    return processSingle(deviceSession, channel, buf);
+                } else if (type.equals("*>A")) {
+                    return processArray(deviceSession, channel, buf);
+                }
+            }
         }
 
         return null;
diff --git a/src/org/traccar/protocol/NoranProtocolDecoder.java b/src/org/traccar/protocol/NoranProtocolDecoder.java
index 2fe680560..c2161d9c9 100644
--- a/src/org/traccar/protocol/NoranProtocolDecoder.java
+++ b/src/org/traccar/protocol/NoranProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.UnitsConverter;
@@ -120,10 +121,11 @@ public class NoranProtocolDecoder extends BaseProtocolDecoder {
                 rawId = buf.readBytes(11);
             }
             String id = rawId.toString(StandardCharsets.US_ASCII).replaceAll("[^\\p{Print}]", "");
-            if (!identify(id, channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             if (newFormat) {
                 DateFormat dateFormat = new SimpleDateFormat("yy-MM-dd HH:mm:ss");
diff --git a/src/org/traccar/protocol/NvsProtocolDecoder.java b/src/org/traccar/protocol/NvsProtocolDecoder.java
index 2a195c599..c32501d56 100644
--- a/src/org/traccar/protocol/NvsProtocolDecoder.java
+++ b/src/org/traccar/protocol/NvsProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
 
@@ -53,13 +54,18 @@ public class NvsProtocolDecoder extends BaseProtocolDecoder {
 
             String imei = buf.toString(buf.readerIndex(), 15, StandardCharsets.US_ASCII);
 
-            if (!identify(imei, channel, remoteAddress)) {
-                sendResponse(channel, "NO01");
-            } else {
+            if (getDeviceSession(channel, remoteAddress, imei) != null) {
                 sendResponse(channel, "OK");
+            } else {
+                sendResponse(channel, "NO01");
             }
 
-        } else if (hasDeviceId()) {
+        } else {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             List<Position> positions = new LinkedList<>();
 
@@ -72,7 +78,7 @@ public class NvsProtocolDecoder extends BaseProtocolDecoder {
             for (int i = 0; i < count; i++) {
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 position.setTime(new Date(buf.readUnsignedInt() * 1000));
 
diff --git a/src/org/traccar/protocol/OrionProtocolDecoder.java b/src/org/traccar/protocol/OrionProtocolDecoder.java
index 0f6d88203..c65e534f4 100644
--- a/src/org/traccar/protocol/OrionProtocolDecoder.java
+++ b/src/org/traccar/protocol/OrionProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
 
@@ -68,7 +69,9 @@ public class OrionProtocolDecoder extends BaseProtocolDecoder {
                 sendResponse(channel, buf);
             }
 
-            if (!identify(String.valueOf(buf.readUnsignedInt()), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(
+                    channel, remoteAddress, String.valueOf(buf.readUnsignedInt()));
+            if (deviceSession == null) {
                 return null;
             }
 
@@ -77,7 +80,7 @@ public class OrionProtocolDecoder extends BaseProtocolDecoder {
             for (int i = 0; i < (header & 0x0f); i++) {
 
                 Position position = new Position();
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
                 position.setProtocol(getProtocolName());
 
                 position.set(Position.KEY_EVENT, buf.readUnsignedByte());
diff --git a/src/org/traccar/protocol/OsmAndProtocolDecoder.java b/src/org/traccar/protocol/OsmAndProtocolDecoder.java
index cea2e6b56..cfa8990dd 100644
--- a/src/org/traccar/protocol/OsmAndProtocolDecoder.java
+++ b/src/org/traccar/protocol/OsmAndProtocolDecoder.java
@@ -25,6 +25,7 @@ import org.jboss.netty.handler.codec.http.HttpVersion;
 import org.jboss.netty.handler.codec.http.QueryStringDecoder;
 import org.joda.time.format.ISODateTimeFormat;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.model.Position;
 
 import java.net.SocketAddress;
@@ -63,10 +64,11 @@ public class OsmAndProtocolDecoder extends BaseProtocolDecoder {
             switch (entry.getKey()) {
                 case "id":
                 case "deviceid":
-                    if (!identify(value, channel, remoteAddress)) {
+                    DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, value);
+                    if (deviceSession == null) {
                         return null;
                     }
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
                     break;
                 case "valid":
                     position.setValid(Boolean.parseBoolean(value));
diff --git a/src/org/traccar/protocol/PathAwayProtocolDecoder.java b/src/org/traccar/protocol/PathAwayProtocolDecoder.java
index bc2f48094..aa2de5704 100644
--- a/src/org/traccar/protocol/PathAwayProtocolDecoder.java
+++ b/src/org/traccar/protocol/PathAwayProtocolDecoder.java
@@ -24,6 +24,7 @@ import org.jboss.netty.handler.codec.http.HttpResponseStatus;
 import org.jboss.netty.handler.codec.http.HttpVersion;
 import org.jboss.netty.handler.codec.http.QueryStringDecoder;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -61,7 +62,9 @@ public class PathAwayProtocolDecoder extends BaseProtocolDecoder {
         HttpRequest request = (HttpRequest) msg;
         QueryStringDecoder decoder = new QueryStringDecoder(request.getUri());
 
-        if (!identify(decoder.getParameters().get("UserName").get(0), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(
+                channel, remoteAddress, decoder.getParameters().get("UserName").get(0));
+        if (deviceSession == null) {
             return null;
         }
 
@@ -72,7 +75,7 @@ public class PathAwayProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/PiligrimProtocolDecoder.java b/src/org/traccar/protocol/PiligrimProtocolDecoder.java
index 48e694b19..47f73fe8f 100644
--- a/src/org/traccar/protocol/PiligrimProtocolDecoder.java
+++ b/src/org/traccar/protocol/PiligrimProtocolDecoder.java
@@ -25,6 +25,7 @@ import org.jboss.netty.handler.codec.http.HttpResponseStatus;
 import org.jboss.netty.handler.codec.http.HttpVersion;
 import org.jboss.netty.handler.codec.http.QueryStringDecoder;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
@@ -79,7 +80,9 @@ public class PiligrimProtocolDecoder extends BaseProtocolDecoder {
             sendResponse(channel, "BINGPS: OK");
 
             QueryStringDecoder decoder = new QueryStringDecoder(request.getUri());
-            if (!identify(decoder.getParameters().get("imei").get(0), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(
+                    channel, remoteAddress, decoder.getParameters().get("imei").get(0));
+            if (deviceSession == null) {
                 return null;
             }
 
@@ -96,7 +99,7 @@ public class PiligrimProtocolDecoder extends BaseProtocolDecoder {
 
                     Position position = new Position();
                     position.setProtocol(getProtocolName());
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
 
                     DateBuilder dateBuilder = new DateBuilder()
                             .setDay(buf.readUnsignedByte())
diff --git a/src/org/traccar/protocol/ProgressProtocolDecoder.java b/src/org/traccar/protocol/ProgressProtocolDecoder.java
index 0439c99db..e524626fa 100644
--- a/src/org/traccar/protocol/ProgressProtocolDecoder.java
+++ b/src/org/traccar/protocol/ProgressProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.model.Position;
 
@@ -78,9 +79,14 @@ public class ProgressProtocolDecoder extends BaseProtocolDecoder {
             buf.skipBytes(length);
             length = buf.readUnsignedShort();
             String imei = buf.readBytes(length).toString(StandardCharsets.US_ASCII);
-            identify(imei, channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, imei);
 
-        } else if (hasDeviceId() && (type == MSG_POINT || type == MSG_ALARM || type == MSG_LOGMSG)) {
+        } else if (type == MSG_POINT || type == MSG_ALARM || type == MSG_LOGMSG) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             List<Position> positions = new LinkedList<>();
 
@@ -92,7 +98,7 @@ public class ProgressProtocolDecoder extends BaseProtocolDecoder {
             for (int j = 0; j < recordCount; j++) {
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 if (type == MSG_LOGMSG) {
                     position.set(Position.KEY_ARCHIVE, true);
diff --git a/src/org/traccar/protocol/Pt3000ProtocolDecoder.java b/src/org/traccar/protocol/Pt3000ProtocolDecoder.java
index 146e3f0a4..88ffb0616 100644
--- a/src/org/traccar/protocol/Pt3000ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Pt3000ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -58,10 +59,11 @@ public class Pt3000ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/Pt502ProtocolDecoder.java b/src/org/traccar/protocol/Pt502ProtocolDecoder.java
index 424d491ae..1436eb5ac 100644
--- a/src/org/traccar/protocol/Pt502ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Pt502ProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 

 import org.jboss.netty.channel.Channel;

 import org.traccar.BaseProtocolDecoder;

+import org.traccar.DeviceSession;

 import org.traccar.helper.DateBuilder;

 import org.traccar.helper.Parser;

 import org.traccar.helper.PatternBuilder;

@@ -77,10 +78,11 @@ public class Pt502ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();

         position.setProtocol(getProtocolName());

 

-        if (!identify(parser.next(), channel, remoteAddress)) {

+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());

+        if (deviceSession == null) {

             return null;

         }

-        position.setDeviceId(getDeviceId());

+        position.setDeviceId(deviceSession.getDeviceId());

 

         DateBuilder dateBuilder = new DateBuilder()

                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt(), parser.nextInt());

diff --git a/src/org/traccar/protocol/RitiProtocolDecoder.java b/src/org/traccar/protocol/RitiProtocolDecoder.java
index b509367bb..bf041554f 100644
--- a/src/org/traccar/protocol/RitiProtocolDecoder.java
+++ b/src/org/traccar/protocol/RitiProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -58,10 +59,11 @@ public class RitiProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(String.valueOf(buf.readUnsignedShort()), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(buf.readUnsignedShort()));
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set("mode", buf.readUnsignedByte());
         position.set("command", buf.readUnsignedByte());
diff --git a/src/org/traccar/protocol/RuptelaProtocolDecoder.java b/src/org/traccar/protocol/RuptelaProtocolDecoder.java
index 0e1ab3d22..a9cea8c64 100644
--- a/src/org/traccar/protocol/RuptelaProtocolDecoder.java
+++ b/src/org/traccar/protocol/RuptelaProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
 
@@ -44,7 +45,8 @@ public class RuptelaProtocolDecoder extends BaseProtocolDecoder {
         buf.readUnsignedShort(); // data length
 
         String imei = String.format("%015d", buf.readLong());
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -59,7 +61,7 @@ public class RuptelaProtocolDecoder extends BaseProtocolDecoder {
             for (int i = 0; i < count; i++) {
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 position.setTime(new Date(buf.readUnsignedInt() * 1000));
                 buf.readUnsignedByte(); // timestamp extension
diff --git a/src/org/traccar/protocol/SanavProtocolDecoder.java b/src/org/traccar/protocol/SanavProtocolDecoder.java
index 156e730a9..103b2d395 100644
--- a/src/org/traccar/protocol/SanavProtocolDecoder.java
+++ b/src/org/traccar/protocol/SanavProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -61,10 +62,11 @@ public class SanavProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/SkypatrolProtocolDecoder.java b/src/org/traccar/protocol/SkypatrolProtocolDecoder.java
index 13e036f0a..d07bb152b 100644
--- a/src/org/traccar/protocol/SkypatrolProtocolDecoder.java
+++ b/src/org/traccar/protocol/SkypatrolProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Log;
@@ -84,10 +85,11 @@ public class SkypatrolProtocolDecoder extends BaseProtocolDecoder {
                 Log.warning("No device id field");
                 return null;
             }
-            if (!identify(id, channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             if (BitUtil.check(mask, 3)) {
                 buf.readUnsignedShort(); // io data
diff --git a/src/org/traccar/protocol/Stl060ProtocolDecoder.java b/src/org/traccar/protocol/Stl060ProtocolDecoder.java
index a966dfea1..b8eb5ed3d 100644
--- a/src/org/traccar/protocol/Stl060ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Stl060ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -78,10 +79,11 @@ public class Stl060ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/SuntechProtocolDecoder.java b/src/org/traccar/protocol/SuntechProtocolDecoder.java
index 5f18fd3ee..5169e7c67 100644
--- a/src/org/traccar/protocol/SuntechProtocolDecoder.java
+++ b/src/org/traccar/protocol/SuntechProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -71,10 +72,11 @@ public class SuntechProtocolDecoder extends BaseProtocolDecoder {
             }
         }
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_VERSION, parser.next());
 
diff --git a/src/org/traccar/protocol/SupermateProtocolDecoder.java b/src/org/traccar/protocol/SupermateProtocolDecoder.java
index bcbd02eb0..f673bff40 100755
--- a/src/org/traccar/protocol/SupermateProtocolDecoder.java
+++ b/src/org/traccar/protocol/SupermateProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -74,10 +75,11 @@ public class SupermateProtocolDecoder extends BaseProtocolDecoder {
         position.setProtocol(getProtocolName());
 
         String imei = parser.next();
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set("commandId", parser.next());
         position.set("command", parser.next());
diff --git a/src/org/traccar/protocol/T55ProtocolDecoder.java b/src/org/traccar/protocol/T55ProtocolDecoder.java
index 87c7a60c3..34efc376f 100644
--- a/src/org/traccar/protocol/T55ProtocolDecoder.java
+++ b/src/org/traccar/protocol/T55ProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.channel.Channel;
 import org.jboss.netty.channel.socket.DatagramChannel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -91,7 +92,8 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
     private Position position = null;
 
-    private Position decodeGprmc(String sentence, SocketAddress remoteAddress, Channel channel) {
+    private Position decodeGprmc(
+            DeviceSession deviceSession, String sentence, SocketAddress remoteAddress, Channel channel) {
 
         if (channel != null && !(channel instanceof DatagramChannel)) {
             channel.write("OK1\r\n");
@@ -105,8 +107,8 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (hasDeviceId()) {
-            position.setDeviceId(getDeviceId());
+        if (deviceSession != null) {
+            position.setDeviceId(deviceSession.getDeviceId());
         }
 
         DateBuilder dateBuilder = new DateBuilder()
@@ -123,13 +125,14 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
         if (parser.hasNext(3)) {
             position.set(Position.KEY_SATELLITES, parser.next());
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
         }
 
-        if (hasDeviceId()) {
+        if (deviceSession != null) {
             return position;
         } else {
             this.position = position; // save position
@@ -137,7 +140,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position decodeGpgga(String sentence) {
+    private Position decodeGpgga(DeviceSession deviceSession, String sentence) {
 
         Parser parser = new Parser(PATTERN_GPGGA, sentence);
         if (!parser.matches()) {
@@ -146,7 +149,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setCurrentDate()
@@ -160,7 +163,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position decodeGprma(String sentence) {
+    private Position decodeGprma(DeviceSession deviceSession, String sentence) {
 
         Parser parser = new Parser(PATTERN_GPRMA, sentence);
         if (!parser.matches()) {
@@ -169,7 +172,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setTime(new Date());
         position.setValid(parser.next().equals("A"));
@@ -181,7 +184,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
         return position;
     }
 
-    private Position decodeTrccr(String sentence) {
+    private Position decodeTrccr(DeviceSession deviceSession, String sentence) {
 
         Parser parser = new Parser(PATTERN_TRCCR, sentence);
         if (!parser.matches()) {
@@ -190,7 +193,7 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
@@ -215,6 +218,8 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
 
         String sentence = (String) msg;
 
+        DeviceSession deviceSession;
+
         if (!sentence.startsWith("$") && sentence.contains("$")) {
             int index = sentence.indexOf("$");
             String id = sentence.substring(0, index);
@@ -223,33 +228,36 @@ public class T55ProtocolDecoder extends BaseProtocolDecoder {
             } else if (id.endsWith("/")) {
                 id = id.substring(id.indexOf('/') + 1, id.length() - 1);
             }
-            identify(id, channel, remoteAddress);
+            deviceSession = getDeviceSession(channel, remoteAddress, id);
             sentence = sentence.substring(index);
+        } else {
+            deviceSession = getDeviceSession(channel, remoteAddress);
         }
 
         if (sentence.startsWith("$PGID")) {
-            identify(sentence.substring(6, sentence.length() - 3), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(6, sentence.length() - 3));
         } else if (sentence.startsWith("$PCPTI")) {
-            identify(sentence.substring(7, sentence.indexOf(",", 7)), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(7, sentence.indexOf(",", 7)));
         } else if (sentence.startsWith("IMEI")) {
-            identify(sentence.substring(5, sentence.length()), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(5, sentence.length()));
         } else if (sentence.startsWith("$GPFID")) {
-            if (identify(sentence.substring(7, sentence.length()), channel, remoteAddress) && position != null) {
+            deviceSession = getDeviceSession(channel, remoteAddress, sentence.substring(7, sentence.length()));
+            if (deviceSession != null && position != null) {
                 Position position = this.position;
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
                 this.position = null;
                 return position;
             }
         } else if (sentence.matches("^[0-9A-F]+$")) {
-            identify(sentence, channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence);
         } else if (sentence.startsWith("$GPRMC")) {
-            return decodeGprmc(sentence, remoteAddress, channel);
-        } else if (sentence.startsWith("$GPGGA") && hasDeviceId()) {
-            return decodeGpgga(sentence);
-        } else if (sentence.startsWith("$GPRMA") && hasDeviceId()) {
-            return decodeGprma(sentence);
-        } else if (sentence.startsWith("$TRCCR") && hasDeviceId()) {
-            return decodeTrccr(sentence);
+            return decodeGprmc(deviceSession, sentence, remoteAddress, channel);
+        } else if (sentence.startsWith("$GPGGA") && deviceSession != null) {
+            return decodeGpgga(deviceSession, sentence);
+        } else if (sentence.startsWith("$GPRMA") && deviceSession != null) {
+            return decodeGprma(deviceSession, sentence);
+        } else if (sentence.startsWith("$TRCCR") && deviceSession != null) {
+            return decodeTrccr(deviceSession, sentence);
         }
 
         return null;
diff --git a/src/org/traccar/protocol/T800xProtocolDecoder.java b/src/org/traccar/protocol/T800xProtocolDecoder.java
index dcf45bb06..de966f901 100644
--- a/src/org/traccar/protocol/T800xProtocolDecoder.java
+++ b/src/org/traccar/protocol/T800xProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BcdUtil;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
@@ -71,7 +72,9 @@ public class T800xProtocolDecoder extends BaseProtocolDecoder {
         int index = buf.readUnsignedShort();
         ChannelBuffer imei = buf.readBytes(8);
 
-        if (!identify(ChannelBuffers.hexDump(imei).substring(1), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(
+                channel, remoteAddress, ChannelBuffers.hexDump(imei).substring(1));
+        if (deviceSession == null) {
             return null;
         }
 
@@ -83,7 +86,7 @@ public class T800xProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set(Position.KEY_INDEX, index);
 
diff --git a/src/org/traccar/protocol/TaipProtocolDecoder.java b/src/org/traccar/protocol/TaipProtocolDecoder.java
index f44b9bcbe..811db774c 100644
--- a/src/org/traccar/protocol/TaipProtocolDecoder.java
+++ b/src/org/traccar/protocol/TaipProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.DateUtil;
 import org.traccar.helper.Parser;
@@ -84,27 +85,6 @@ public class TaipProtocolDecoder extends BaseProtocolDecoder {
             sentence = sentence.substring(beginIndex + 1);
         }
 
-        // Find device identifier
-        beginIndex = sentence.indexOf(";ID=");
-        if (beginIndex != -1) {
-            beginIndex += 4;
-            int endIndex = sentence.indexOf(';', beginIndex);
-            if (endIndex == -1) {
-                endIndex = sentence.length();
-            }
-
-            String id = sentence.substring(beginIndex, endIndex);
-            if (!identify(id, channel, remoteAddress)) {
-                return null;
-            }
-
-            if (sendResponse && channel != null) {
-                channel.write(id);
-            }
-        } else {
-            return null;
-        }
-
         Parser parser = new Parser(PATTERN, sentence);
         if (!parser.matches()) {
             return null;
@@ -112,7 +92,6 @@ public class TaipProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
 
         String week = parser.next();
         String day = parser.next();
@@ -157,8 +136,9 @@ public class TaipProtocolDecoder extends BaseProtocolDecoder {
                     switch (key) {
 
                         case "id":
-                            if (!identify(value, channel, remoteAddress)) {
-                                return null;
+                            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, value);
+                            if (deviceSession != null) {
+                                position.setDeviceId(deviceSession.getDeviceId());
                             }
                             if (sendResponse && channel != null) {
                                 channel.write(value);
@@ -186,7 +166,10 @@ public class TaipProtocolDecoder extends BaseProtocolDecoder {
             }
         }
 
-        return position;
+        if (position.getDeviceId() != 0) {
+            return position;
+        }
+        return null;
     }
 
 }
diff --git a/src/org/traccar/protocol/TelicProtocolDecoder.java b/src/org/traccar/protocol/TelicProtocolDecoder.java
index be4c80b84..818390f60 100644
--- a/src/org/traccar/protocol/TelicProtocolDecoder.java
+++ b/src/org/traccar/protocol/TelicProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -69,10 +70,11 @@ public class TelicProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_TYPE, parser.next());
 
diff --git a/src/org/traccar/protocol/TeltonikaProtocolDecoder.java b/src/org/traccar/protocol/TeltonikaProtocolDecoder.java
index eb77cf350..d982b07b3 100644
--- a/src/org/traccar/protocol/TeltonikaProtocolDecoder.java
+++ b/src/org/traccar/protocol/TeltonikaProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -39,11 +40,11 @@ public class TeltonikaProtocolDecoder extends BaseProtocolDecoder {
 
         int length = buf.readUnsignedShort();
         String imei = buf.toString(buf.readerIndex(), length, StandardCharsets.US_ASCII);
-        boolean result =  identify(imei, channel, remoteAddress);
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
 
         if (channel != null) {
             ChannelBuffer response = ChannelBuffers.directBuffer(1);
-            if (result) {
+            if (deviceSession != null) {
                 response.writeByte(1);
             } else {
                 response.writeByte(0);
@@ -187,7 +188,7 @@ public class TeltonikaProtocolDecoder extends BaseProtocolDecoder {
 
     }
 
-    private List<Position> parseData(Channel channel, ChannelBuffer buf) {
+    private List<Position> parseData(Channel channel, SocketAddress remoteAddress, ChannelBuffer buf) {
         List<Position> positions = new LinkedList<>();
 
         buf.skipBytes(4); // marker
@@ -195,11 +196,16 @@ public class TeltonikaProtocolDecoder extends BaseProtocolDecoder {
         int codec = buf.readUnsignedByte();
         int count = buf.readUnsignedByte();
 
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
+            return null;
+        }
+
         for (int i = 0; i < count; i++) {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             if (codec == CODEC_12) {
                 decodeSerial(position, buf);
@@ -228,7 +234,7 @@ public class TeltonikaProtocolDecoder extends BaseProtocolDecoder {
         if (buf.getUnsignedShort(0) > 0) {
             parseIdentification(channel, remoteAddress, buf);
         } else {
-            return parseData(channel, buf);
+            return parseData(channel, remoteAddress, buf);
         }
 
         return null;
diff --git a/src/org/traccar/protocol/ThinkRaceProtocolDecoder.java b/src/org/traccar/protocol/ThinkRaceProtocolDecoder.java
index c7236dc6d..2c49cccaf 100644
--- a/src/org/traccar/protocol/ThinkRaceProtocolDecoder.java
+++ b/src/org/traccar/protocol/ThinkRaceProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.model.Position;
 
@@ -63,7 +64,8 @@ public class ThinkRaceProtocolDecoder extends BaseProtocolDecoder {
 
             if (command == 0x01) {
                 String imei = buf.toString(buf.readerIndex(), 15, StandardCharsets.US_ASCII);
-                if (identify(imei, channel, remoteAddress) && channel != null) {
+                DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+                if (deviceSession != null && channel != null) {
                     ChannelBuffer response = ChannelBuffers.dynamicBuffer();
                     response.writeByte(0x48); response.writeByte(0x52); // header
                     response.writeBytes(id);
@@ -76,11 +78,16 @@ public class ThinkRaceProtocolDecoder extends BaseProtocolDecoder {
                 }
             }
 
-        } else if (hasDeviceId() && type == MSG_GPS) {
+        } else if (type == MSG_GPS) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.setTime(new Date(buf.readUnsignedInt() * 1000));
 
diff --git a/src/org/traccar/protocol/Tk102ProtocolDecoder.java b/src/org/traccar/protocol/Tk102ProtocolDecoder.java
index 8323d6a3d..bb7510eb1 100644
--- a/src/org/traccar/protocol/Tk102ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tk102ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -58,14 +59,17 @@ public class Tk102ProtocolDecoder extends BaseProtocolDecoder {
 
         if (sentence.startsWith("[!")) {
 
-            if (!identify(sentence.substring(14, 14 + 15), channel, remoteAddress)) {
-                return null;
-            }
-            if (channel != null) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, sentence.substring(14, 14 + 15));
+            if (deviceSession != null && channel != null) {
                 channel.write("[”0000000001" + sentence.substring(13) + "]");
             }
 
-        } else if (hasDeviceId()) {
+        } else {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+            if (deviceSession == null) {
+                return null;
+            }
 
             Parser parser = new Parser(PATTERN, sentence);
             if (!parser.matches()) {
@@ -74,7 +78,7 @@ public class Tk102ProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/Tk103ProtocolDecoder.java b/src/org/traccar/protocol/Tk103ProtocolDecoder.java
index a22eaa4ba..a0998d50d 100644
--- a/src/org/traccar/protocol/Tk103ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tk103ProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
@@ -103,10 +104,11 @@ public class Tk103ProtocolDecoder extends BaseProtocolDecoder {
 
         Parser parser = new Parser(PATTERN_BATTERY, sentence);
         if (parser.matches()) {
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
@@ -129,10 +131,11 @@ public class Tk103ProtocolDecoder extends BaseProtocolDecoder {
 
         parser = new Parser(PATTERN_NETWORK, sentence);
         if (parser.matches()) {
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             getLastLocation(position, null);
 
@@ -149,10 +152,11 @@ public class Tk103ProtocolDecoder extends BaseProtocolDecoder {
             return null;
         }
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         int alarm = sentence.indexOf("BO01");
         if (alarm != -1) {
diff --git a/src/org/traccar/protocol/Tlt2hProtocolDecoder.java b/src/org/traccar/protocol/Tlt2hProtocolDecoder.java
index d7cc74e84..6a58d6dcb 100644
--- a/src/org/traccar/protocol/Tlt2hProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tlt2hProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -69,7 +70,8 @@ public class Tlt2hProtocolDecoder extends BaseProtocolDecoder {
             return null;
         }
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
 
@@ -84,7 +86,7 @@ public class Tlt2hProtocolDecoder extends BaseProtocolDecoder {
 
                 Position position = new Position();
                 position.setProtocol(getProtocolName());
-                position.setDeviceId(getDeviceId());
+                position.setDeviceId(deviceSession.getDeviceId());
 
                 parser.next(); // base station info
 
diff --git a/src/org/traccar/protocol/TopflytechProtocolDecoder.java b/src/org/traccar/protocol/TopflytechProtocolDecoder.java
index 7333c4c86..04f379557 100644
--- a/src/org/traccar/protocol/TopflytechProtocolDecoder.java
+++ b/src/org/traccar/protocol/TopflytechProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -56,10 +57,11 @@ public class TopflytechProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/TotemProtocolDecoder.java b/src/org/traccar/protocol/TotemProtocolDecoder.java
index 1e07e7ed5..7b196f5ad 100644
--- a/src/org/traccar/protocol/TotemProtocolDecoder.java
+++ b/src/org/traccar/protocol/TotemProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -185,10 +186,11 @@ public class TotemProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (pattern == PATTERN1 || pattern == PATTERN2) {
 
diff --git a/src/org/traccar/protocol/Tr20ProtocolDecoder.java b/src/org/traccar/protocol/Tr20ProtocolDecoder.java
index de16fafb6..54b303b5d 100644
--- a/src/org/traccar/protocol/Tr20ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tr20ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -73,10 +74,11 @@ public class Tr20ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.next().equals("A"));
 
diff --git a/src/org/traccar/protocol/Tr900ProtocolDecoder.java b/src/org/traccar/protocol/Tr900ProtocolDecoder.java
index 8659861d8..8dfff9e41 100644
--- a/src/org/traccar/protocol/Tr900ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tr900ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -66,10 +67,11 @@ public class Tr900ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.nextInt() == 1);
 
diff --git a/src/org/traccar/protocol/TrackboxProtocolDecoder.java b/src/org/traccar/protocol/TrackboxProtocolDecoder.java
index 369409fc9..89253b891 100644
--- a/src/org/traccar/protocol/TrackboxProtocolDecoder.java
+++ b/src/org/traccar/protocol/TrackboxProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -59,12 +60,17 @@ public class TrackboxProtocolDecoder extends BaseProtocolDecoder {
 
         if (sentence.startsWith("a=connect")) {
             String id = sentence.substring(sentence.indexOf("i=") + 2);
-            if (identify(id, channel, remoteAddress)) {
+            if (getDeviceSession(channel, remoteAddress, id) != null) {
                 sendResponse(channel);
             }
             return null;
         }
 
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
+            return null;
+        }
+
         Parser parser = new Parser(PATTERN, sentence);
         if (!parser.matches()) {
             return null;
@@ -72,8 +78,8 @@ public class TrackboxProtocolDecoder extends BaseProtocolDecoder {
         sendResponse(channel);
 
         Position position = new Position();
-        position.setDeviceId(getDeviceId());
         position.setProtocol(getProtocolName());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/TramigoProtocolDecoder.java b/src/org/traccar/protocol/TramigoProtocolDecoder.java
index be276a5f7..af81616d8 100644
--- a/src/org/traccar/protocol/TramigoProtocolDecoder.java
+++ b/src/org/traccar/protocol/TramigoProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -63,10 +64,11 @@ public class TramigoProtocolDecoder extends BaseProtocolDecoder {
         position.set(Position.KEY_INDEX, index);
         position.setValid(true);
 
-        if (!identify(String.valueOf(id), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, String.valueOf(id));
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (protocol == 0x01 && (type == MSG_COMPACT || type == MSG_FULL)) {
 
diff --git a/src/org/traccar/protocol/TrvProtocolDecoder.java b/src/org/traccar/protocol/TrvProtocolDecoder.java
index 8b35805a4..42f8d313c 100644
--- a/src/org/traccar/protocol/TrvProtocolDecoder.java
+++ b/src/org/traccar/protocol/TrvProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -81,11 +82,12 @@ public class TrvProtocolDecoder extends BaseProtocolDecoder {
         }
 
         if (type.equals("AP00")) {
-            identify(sentence.substring(7), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(7));
             return null;
         }
 
-        if (!hasDeviceId()) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -98,7 +100,7 @@ public class TrvProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             getLastLocation(position, null);
 
@@ -121,7 +123,7 @@ public class TrvProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/Tt8850ProtocolDecoder.java b/src/org/traccar/protocol/Tt8850ProtocolDecoder.java
index 614522f2b..39fedc138 100644
--- a/src/org/traccar/protocol/Tt8850ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Tt8850ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -70,10 +71,11 @@ public class Tt8850ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.setValid(parser.nextInt() < 20);
         position.setSpeed(UnitsConverter.knotsFromKph(parser.nextDouble()));
diff --git a/src/org/traccar/protocol/TytanProtocolDecoder.java b/src/org/traccar/protocol/TytanProtocolDecoder.java
index b657ae029..092ba431a 100644
--- a/src/org/traccar/protocol/TytanProtocolDecoder.java
+++ b/src/org/traccar/protocol/TytanProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.Position;
@@ -136,7 +137,8 @@ public class TytanProtocolDecoder extends BaseProtocolDecoder {
         }
 
         String id = String.valueOf(buf.readUnsignedInt());
-        if (!identify(id, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -146,7 +148,7 @@ public class TytanProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             int end = buf.readerIndex() + buf.readUnsignedByte();
 
diff --git a/src/org/traccar/protocol/TzoneProtocolDecoder.java b/src/org/traccar/protocol/TzoneProtocolDecoder.java
index f4d6c68f3..be4919dc2 100644
--- a/src/org/traccar/protocol/TzoneProtocolDecoder.java
+++ b/src/org/traccar/protocol/TzoneProtocolDecoder.java
@@ -19,6 +19,7 @@ import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.DateBuilder;
 import org.traccar.model.Position;
@@ -46,7 +47,8 @@ public class TzoneProtocolDecoder extends BaseProtocolDecoder {
         buf.readUnsignedInt(); // firmware
 
         String imei = ChannelBuffers.hexDump(buf.readBytes(8)).substring(1);
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -54,7 +56,7 @@ public class TzoneProtocolDecoder extends BaseProtocolDecoder {
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         // GPS info
 
diff --git a/src/org/traccar/protocol/UlbotechProtocolDecoder.java b/src/org/traccar/protocol/UlbotechProtocolDecoder.java
index 2fd7d8f74..c17341b5f 100644
--- a/src/org/traccar/protocol/UlbotechProtocolDecoder.java
+++ b/src/org/traccar/protocol/UlbotechProtocolDecoder.java
@@ -20,6 +20,7 @@ import org.jboss.netty.buffer.ChannelBuffers;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
 import org.traccar.Context;
+import org.traccar.DeviceSession;
 import org.traccar.helper.BitUtil;
 import org.traccar.helper.ObdDecoder;
 import org.traccar.helper.UnitsConverter;
@@ -131,10 +132,11 @@ public class UlbotechProtocolDecoder extends BaseProtocolDecoder {
         position.setProtocol(getProtocolName());
 
         String imei = ChannelBuffers.hexDump(buf.readBytes(8)).substring(1);
-        if (!identify(imei, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         long seconds = buf.readUnsignedInt() & 0x7fffffffL;
         seconds += 946684800L; // 2000-01-01 00:00
diff --git a/src/org/traccar/protocol/UproProtocolDecoder.java b/src/org/traccar/protocol/UproProtocolDecoder.java
index f7166e589..b4000c37a 100644
--- a/src/org/traccar/protocol/UproProtocolDecoder.java
+++ b/src/org/traccar/protocol/UproProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -56,10 +57,11 @@ public class UproProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setTime(parser.nextInt(), parser.nextInt(), parser.nextInt());
diff --git a/src/org/traccar/protocol/V680ProtocolDecoder.java b/src/org/traccar/protocol/V680ProtocolDecoder.java
index 35bd3780b..29ac4fd90 100644
--- a/src/org/traccar/protocol/V680ProtocolDecoder.java
+++ b/src/org/traccar/protocol/V680ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -62,7 +63,7 @@ public class V680ProtocolDecoder extends BaseProtocolDecoder {
 
         if (sentence.length() == 16) {
 
-            identify(sentence.substring(1, sentence.length()), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, sentence.substring(1, sentence.length()));
 
         } else {
 
@@ -74,13 +75,16 @@ public class V680ProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
+            DeviceSession deviceSession;
             if (parser.hasNext()) {
-                identify(parser.next(), channel, remoteAddress);
+                deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            } else {
+                deviceSession = getDeviceSession(channel, remoteAddress);
             }
-            if (!hasDeviceId()) {
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             position.set("user", parser.next());
             position.setValid(parser.nextInt() > 0);
diff --git a/src/org/traccar/protocol/VisiontekProtocolDecoder.java b/src/org/traccar/protocol/VisiontekProtocolDecoder.java
index 5d9b905f1..bfd4a78fa 100644
--- a/src/org/traccar/protocol/VisiontekProtocolDecoder.java
+++ b/src/org/traccar/protocol/VisiontekProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -80,12 +81,11 @@ public class VisiontekProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        String id = parser.next();
-        String imei = parser.next();
-        if (!identify(id, channel, remoteAddress, false) && (imei == null || !identify(imei, channel, remoteAddress))) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next(), parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/WatchProtocolDecoder.java b/src/org/traccar/protocol/WatchProtocolDecoder.java
index b9b42332f..ca63e701e 100644
--- a/src/org/traccar/protocol/WatchProtocolDecoder.java
+++ b/src/org/traccar/protocol/WatchProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -79,7 +80,8 @@ public class WatchProtocolDecoder extends BaseProtocolDecoder {
 
         String manufacturer = parser.next();
         String id = parser.next();
-        if (!identify(id, channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
+        if (deviceSession == null) {
             return null;
         }
 
@@ -95,7 +97,7 @@ public class WatchProtocolDecoder extends BaseProtocolDecoder {
                 if (values.length >= 4) {
                     Position position = new Position();
                     position.setProtocol(getProtocolName());
-                    position.setDeviceId(getDeviceId());
+                    position.setDeviceId(deviceSession.getDeviceId());
 
                     getLastLocation(position, null);
 
@@ -118,7 +120,7 @@ public class WatchProtocolDecoder extends BaseProtocolDecoder {
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/WialonProtocolDecoder.java b/src/org/traccar/protocol/WialonProtocolDecoder.java
index 1de2f9dbf..627b93b1c 100644
--- a/src/org/traccar/protocol/WialonProtocolDecoder.java
+++ b/src/org/traccar/protocol/WialonProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -66,16 +67,21 @@ public class WialonProtocolDecoder extends BaseProtocolDecoder {
         }
     }
 
-    private Position decodePosition(String substring) {
+    private Position decodePosition(Channel channel, SocketAddress remoteAddress, String substring) {
+
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
+        if (deviceSession == null) {
+            return null;
+        }
 
         Parser parser = new Parser(PATTERN, substring);
-        if (!hasDeviceId() || !parser.matches()) {
+        if (!parser.matches()) {
             return null;
         }
 
         Position position = new Position();
         position.setProtocol(getProtocolName());
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDateReverse(parser.nextInt(), parser.nextInt(), parser.nextInt())
@@ -129,7 +135,8 @@ public class WialonProtocolDecoder extends BaseProtocolDecoder {
         if (sentence.startsWith("#L#")) {
 
             String imei = sentence.substring(3, sentence.indexOf(';'));
-            if (identify(imei, channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, imei);
+            if (deviceSession != null) {
                 sendResponse(channel, "#AL#", 1);
             }
 
@@ -140,7 +147,7 @@ public class WialonProtocolDecoder extends BaseProtocolDecoder {
         } else if (sentence.startsWith("#SD#") || sentence.startsWith("#D#")) {
 
             Position position = decodePosition(
-                    sentence.substring(sentence.indexOf('#', 1) + 1));
+                    channel, remoteAddress, sentence.substring(sentence.indexOf('#', 1) + 1));
 
             if (position != null) {
                 sendResponse(channel, "#AD#", 1);
@@ -153,7 +160,7 @@ public class WialonProtocolDecoder extends BaseProtocolDecoder {
             List<Position> positions = new LinkedList<>();
 
             for (String message : messages) {
-                Position position = decodePosition(message);
+                Position position = decodePosition(channel, remoteAddress, message);
                 if (position != null) {
                     positions.add(position);
                 }
diff --git a/src/org/traccar/protocol/WondexProtocolDecoder.java b/src/org/traccar/protocol/WondexProtocolDecoder.java
index 81aeff54e..d048b9b31 100644
--- a/src/org/traccar/protocol/WondexProtocolDecoder.java
+++ b/src/org/traccar/protocol/WondexProtocolDecoder.java
@@ -18,6 +18,7 @@ package org.traccar.protocol;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -65,15 +66,17 @@ public class WondexProtocolDecoder extends BaseProtocolDecoder {
         if (buf.getUnsignedByte(0) == 0xD0) {
 
             long deviceId = ((Long.reverseBytes(buf.getLong(0))) >> 32) & 0xFFFFFFFFL;
-            identify(String.valueOf(deviceId), channel, remoteAddress);
+            getDeviceSession(channel, remoteAddress, String.valueOf(deviceId));
 
             return null;
         } else if (buf.toString(StandardCharsets.US_ASCII).startsWith("$OK:")
-            || buf.toString(StandardCharsets.US_ASCII).startsWith("$ERR:")) {
+                || buf.toString(StandardCharsets.US_ASCII).startsWith("$ERR:")) {
+
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress);
 
             Position position = new Position();
             position.setProtocol(getProtocolName());
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
             getLastLocation(position, new Date());
             position.setValid(false);
             position.set(Position.KEY_RESULT, buf.toString(StandardCharsets.US_ASCII));
@@ -89,10 +92,11 @@ public class WondexProtocolDecoder extends BaseProtocolDecoder {
             Position position = new Position();
             position.setProtocol(getProtocolName());
 
-            if (!identify(parser.next(), channel, remoteAddress)) {
+            DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+            if (deviceSession == null) {
                 return null;
             }
-            position.setDeviceId(getDeviceId());
+            position.setDeviceId(deviceSession.getDeviceId());
 
             DateBuilder dateBuilder = new DateBuilder()
                     .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/XexunProtocolDecoder.java b/src/org/traccar/protocol/XexunProtocolDecoder.java
index 82dc16d11..7b6a84f1f 100644
--- a/src/org/traccar/protocol/XexunProtocolDecoder.java
+++ b/src/org/traccar/protocol/XexunProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -100,10 +101,11 @@ public class XexunProtocolDecoder extends BaseProtocolDecoder {
         position.set("signal", parser.next());
         position.set(Position.KEY_ALARM, parser.next());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         if (full) {
             position.set(Position.KEY_SATELLITES, parser.next().replaceFirst("^0*(?![\\.$])", ""));
diff --git a/src/org/traccar/protocol/XirgoProtocolDecoder.java b/src/org/traccar/protocol/XirgoProtocolDecoder.java
index 415d8dee3..5006102e6 100644
--- a/src/org/traccar/protocol/XirgoProtocolDecoder.java
+++ b/src/org/traccar/protocol/XirgoProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -109,10 +110,11 @@ public class XirgoProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         position.set(Position.KEY_EVENT, parser.next());
 
diff --git a/src/org/traccar/protocol/Xt013ProtocolDecoder.java b/src/org/traccar/protocol/Xt013ProtocolDecoder.java
index 1c0726d8c..b5c222ba6 100644
--- a/src/org/traccar/protocol/Xt013ProtocolDecoder.java
+++ b/src/org/traccar/protocol/Xt013ProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -68,10 +69,11 @@ public class Xt013ProtocolDecoder extends BaseProtocolDecoder {
         Position position = new Position();
         position.setProtocol(getProtocolName());
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())
diff --git a/src/org/traccar/protocol/YwtProtocolDecoder.java b/src/org/traccar/protocol/YwtProtocolDecoder.java
index b653c1ec4..da5a86175 100644
--- a/src/org/traccar/protocol/YwtProtocolDecoder.java
+++ b/src/org/traccar/protocol/YwtProtocolDecoder.java
@@ -17,6 +17,7 @@ package org.traccar.protocol;
 
 import org.jboss.netty.channel.Channel;
 import org.traccar.BaseProtocolDecoder;
+import org.traccar.DeviceSession;
 import org.traccar.helper.DateBuilder;
 import org.traccar.helper.Parser;
 import org.traccar.helper.PatternBuilder;
@@ -81,10 +82,11 @@ public class YwtProtocolDecoder extends BaseProtocolDecoder {
 
         String type = parser.next();
 
-        if (!identify(parser.next(), channel, remoteAddress)) {
+        DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, parser.next());
+        if (deviceSession == null) {
             return null;
         }
-        position.setDeviceId(getDeviceId());
+        position.setDeviceId(deviceSession.getDeviceId());
 
         DateBuilder dateBuilder = new DateBuilder()
                 .setDate(parser.nextInt(), parser.nextInt(), parser.nextInt())