Handle Snapper protocol ping

3 files changed, 54 insertions, 5 deletions

diff --git a/src/main/java/org/traccar/protocol/SnapperFrameDecoder.java b/src/main/java/org/traccar/protocol/SnapperFrameDecoder.java
new file mode 100644
index 000000000..be45346a6
--- /dev/null
+++ b/src/main/java/org/traccar/protocol/SnapperFrameDecoder.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2024 Anton Tananaev (anton@traccar.org)
+ *
+ * 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.protocol;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelHandlerContext;
+import org.traccar.BaseFrameDecoder;
+
+public class SnapperFrameDecoder extends BaseFrameDecoder {
+
+    @Override
+    protected Object decode(
+            ChannelHandlerContext ctx, Channel channel, ByteBuf buf) throws Exception {
+
+        byte header = buf.getByte(buf.readerIndex());
+        if (header == 'P') {
+            if (buf.readableBytes() >= 2) {
+                return buf.readRetainedSlice(2);
+            }
+        } else if (buf.readableBytes() >= 16) {
+            int length = buf.getIntLE(buf.readerIndex() + 12) + 12 + 4 + 9;
+            if (buf.readableBytes() >= length) {
+                return buf.readRetainedSlice(length);
+            }
+        }
+
+        return null;
+    }
+
+}
diff --git a/src/main/java/org/traccar/protocol/SnapperProtocol.java b/src/main/java/org/traccar/protocol/SnapperProtocol.java
index 2e294eac6..25a11ed3a 100644
--- a/src/main/java/org/traccar/protocol/SnapperProtocol.java
+++ b/src/main/java/org/traccar/protocol/SnapperProtocol.java
@@ -15,15 +15,12 @@
  */
 package org.traccar.protocol;
 
-import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
 import jakarta.inject.Inject;
 import org.traccar.BaseProtocol;
 import org.traccar.PipelineBuilder;
 import org.traccar.TrackerServer;
 import org.traccar.config.Config;
 
-import java.nio.ByteOrder;
-
 public class SnapperProtocol extends BaseProtocol {
 
     @Inject
@@ -31,7 +28,7 @@ public class SnapperProtocol extends BaseProtocol {
         addServer(new TrackerServer(config, getName(), false) {
             @Override
             protected void addProtocolHandlers(PipelineBuilder pipeline, Config config) {
-                pipeline.addLast(new LengthFieldBasedFrameDecoder(ByteOrder.LITTLE_ENDIAN, 1024, 12, 4, 9, 0, true));
+                pipeline.addLast(new SnapperFrameDecoder());
                 pipeline.addLast(new SnapperProtocolDecoder(SnapperProtocol.this));
             }
         });
diff --git a/src/main/java/org/traccar/protocol/SnapperProtocolDecoder.java b/src/main/java/org/traccar/protocol/SnapperProtocolDecoder.java
index e60736667..ef1a4426a 100644
--- a/src/main/java/org/traccar/protocol/SnapperProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/SnapperProtocolDecoder.java
@@ -150,7 +150,15 @@ public class SnapperProtocolDecoder extends BaseProtocolDecoder {
 
         ByteBuf buf = (ByteBuf) msg;
 
-        buf.readUnsignedByte(); // header
+        byte header = buf.readByte();
+        if (header == 'P') {
+            if (channel != null) {
+                ByteBuf response = Unpooled.wrappedBuffer(new byte[] {0x50, 0x4f});
+                channel.writeAndFlush(new NetworkMessage(response, remoteAddress));
+            }
+            return null;
+        }
+
         buf.readUnsignedByte(); // protocol version
         buf.readUnsignedIntLE(); // system bonus identifier