Fix frame decoding

3 files changed, 10 insertions, 2 deletions

diff --git a/src/main/java/org/traccar/protocol/Jt600FrameDecoder.java b/src/main/java/org/traccar/protocol/Jt600FrameDecoder.java
index b5d060ecc..bfefb94a7 100644
--- a/src/main/java/org/traccar/protocol/Jt600FrameDecoder.java
+++ b/src/main/java/org/traccar/protocol/Jt600FrameDecoder.java
@@ -35,7 +35,7 @@ public class Jt600FrameDecoder extends BaseFrameDecoder {
         char type = (char) buf.getByte(buf.readerIndex());
 
         if (type == '$') {
-            boolean longFormat = buf.getUnsignedByte(buf.readerIndex() + 1) == 0x75;
+            boolean longFormat = Jt600ProtocolDecoder.isLongFormat(buf, buf.readerIndex() + 1);
             int length = buf.getUnsignedShort(buf.readerIndex() + (longFormat ? 8 : 7)) + 10;
             if (length <= buf.readableBytes()) {
                 return buf.readRetainedSlice(length);
diff --git a/src/main/java/org/traccar/protocol/Jt600ProtocolDecoder.java b/src/main/java/org/traccar/protocol/Jt600ProtocolDecoder.java
index 82abeb42e..f456cd1ef 100644
--- a/src/main/java/org/traccar/protocol/Jt600ProtocolDecoder.java
+++ b/src/main/java/org/traccar/protocol/Jt600ProtocolDecoder.java
@@ -86,13 +86,17 @@ public class Jt600ProtocolDecoder extends BaseProtocolDecoder {
 
     }
 
+    static boolean isLongFormat(ByteBuf buf, int flagIndex) {
+        return buf.getUnsignedByte(flagIndex) >> 4 == 0x7;
+    }
+
     private List<Position> decodeBinary(ByteBuf buf, Channel channel, SocketAddress remoteAddress) {
 
         List<Position> positions = new LinkedList<>();
 
         buf.readByte(); // header
 
-        boolean longFormat = buf.getUnsignedByte(buf.readerIndex()) >> 4 == 0x7;
+        boolean longFormat = isLongFormat(buf, buf.readerIndex());
 
         String id = String.valueOf(Long.parseLong(ByteBufUtil.hexDump(buf.readSlice(5))));
         DeviceSession deviceSession = getDeviceSession(channel, remoteAddress, id);
diff --git a/src/test/java/org/traccar/protocol/Jt600FrameDecoderTest.java b/src/test/java/org/traccar/protocol/Jt600FrameDecoderTest.java
index ae0948987..e695624a9 100644
--- a/src/test/java/org/traccar/protocol/Jt600FrameDecoderTest.java
+++ b/src/test/java/org/traccar/protocol/Jt600FrameDecoderTest.java
@@ -11,6 +11,10 @@ public class Jt600FrameDecoderTest extends ProtocolTest {
         Jt600FrameDecoder decoder = new Jt600FrameDecoder();
 
         verifyFrame(
+                binary("2478905197081711003405101917164812492365028134847d0a1c000002640c0000000020c032759600731000000f0f0f0f0f0f0f0f0f0f000702850274"),
+                decoder.decode(null, null, binary("2478905197081711003405101917164812492365028134847d0a1c000002640c0000000020c032759600731000000f0f0f0f0f0f0f0f0f0f000702850274")));
+
+        verifyFrame(
                 binary("24315011626912001b21111718095900000000000000000e0000005c000000000000000000"),
                 decoder.decode(null, null, binary("24315011626912001b21111718095900000000000000000e0000005c00000000000000000024315011626912001b22111708130400000000000000000e0000005a00000000000000000024315011626912001b22111708140400000000000000000e0000005a000000723e18a61b01")));