1 files changed, 14 insertions, 7 deletions
diff --git a/src/main/java/org/traccar/protocol/Xexun2ProtocolDecoder.java b/src/main/java/org/traccar/protocol/Xexun2ProtocolDecoder.java
index 28e7fbda3..913dfaf28 100644
--- a/src/main/java/org/traccar/protocol/Xexun2ProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/Xexun2ProtocolDecoder.java
@@ -24,6 +24,7 @@ import org.traccar.session.DeviceSession;
 import org.traccar.NetworkMessage;
 import org.traccar.Protocol;
 import org.traccar.helper.BitUtil;
+import org.traccar.helper.Checksum;
 import org.traccar.helper.UnitsConverter;
 import org.traccar.model.CellTower;
 import org.traccar.model.Network;
@@ -41,13 +42,14 @@ public class Xexun2ProtocolDecoder extends BaseProtocolDecoder {
         super(protocol);
     }
 
+    public static final int FLAG = 0xfaaf;
+    public static final int MSG_COMMAND = 0x07;
     public static final int MSG_POSITION = 0x14;
 
     private void sendResponse(Channel channel, int type, int index, ByteBuf imei) {
         if (channel != null) {
             ByteBuf response = Unpooled.buffer();
-            response.writeByte(0xfa);
-            response.writeByte(0xaf);
+            response.writeShort(FLAG);
 
             response.writeShort(type);
             response.writeShort(index);
@@ -56,8 +58,7 @@ public class Xexun2ProtocolDecoder extends BaseProtocolDecoder {
             response.writeShort(0xfffe); // checksum
             response.writeByte(1); // response
 
-            response.writeByte(0xfa);
-            response.writeByte(0xaf);
+            response.writeShort(FLAG);
 
             channel.writeAndFlush(new NetworkMessage(response, channel.remoteAddress()));
         }
@@ -99,10 +100,16 @@ public class Xexun2ProtocolDecoder extends BaseProtocolDecoder {
             return null;
         }
 
-        sendResponse(channel, type, index, imei);
+        int payloadSize = buf.readUnsignedShort() & 0x03ff;
+        int checksum = buf.readUnsignedShort();
 
-        buf.readUnsignedShort(); // attributes
-        buf.readUnsignedShort(); // checksum
+        if (checksum != Checksum.ip(buf.nioBuffer(buf.readerIndex(), payloadSize))) {
+            return null;
+        }
+
+        if (type != MSG_COMMAND) {
+            sendResponse(channel, type, index, imei);
+        }
 
         if (type == MSG_POSITION) {
             List<Integer> lengths = new ArrayList<>();