Meitrack T711L – Decoder error (IndexOutOfBoundsException) with valid protocol data

Hello,

I am experiencing a decoding issue with a Meitrack device (T711L) on Traccar 6.12.2.

Environment:

• Traccar version: 6.12.2
• Java: 21 (OpenJDK)
• OS: Linux (CentOS 7)
• Database: MySQL

The server starts correctly and receives data from multiple devices.
However, for one Meitrack device, I get the following error:

2026-04-04 00:12:02  INFO: [T29f9af92: meitrack < 105.71.4.209] 242466313039352c3836373935313037383031303536342c4343452cfd0b000003005d0117000705010611071914001501fe69641b000808180009c6000a05000b4c0016070019a6011a91054021000502f5a90502037a7296ff04a5ec62310cb2e907000d3f800200030e0c5c0202001705213e9701a0ff4b02fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff8280201ff620118000705010611071914001501fe69641b000808180009c7000a05000b4d0016060019a1011a8d054023000602bba9050203637296ff04a7ec62310cb2e907000d418002001c01000000030e0c5c0202001705213e9701a0ff4b02fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff8280201ff620118000705010611071914001501fe69641b0008081c0009cd000a05000b4d0016080019a1011a8d0540230006023ba9050203297296ff04a9ec62310cc7e907000d438002001c01000000030e0c5c0202001705213e9701a0ff4b02fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff8280201ff2a41440d0a
2026-04-04 00:12:02  WARN: [T29f9af92] error - readerIndex(1101) + length(2) exceeds writerIndex(1102): UnpooledSlicedByteBuf(ridx: 1101, widx: 1102, cap: 1102/1102, unwrapped: AdaptivePoolingAllocator$AdaptiveByteBuf(ridx: 1102, widx: 1102, cap: 2048)) - IndexOutOfBoundsException (... < MeitrackProtocolDecoder:411 < *:584 < ExtendedObjectDecoder:73 < ... < WrapperContext:102 < ... < WrapperInboundHandler:56 < ...)
2026-04-04 00:12:02  INFO: [T29f9af92] disconnected

The device connects successfully and sends data, but this specific message causes a decoding failure.

Protocol documentation:
https://www.meitrack.com/cd-download/Protocols/MEITRACK_T711L_GPRS_Protocol.pdf

Should this be reported as a bug in the decoder?

Any help or guidance would be appreciated.

Thank you.

This should fix the problem:

https://github.com/traccar/traccar/commit/c0c1fa432349c3e30e3da93c3e2d9fa6279faefd

Hi Anton,

Thank you so much for your quick response and for providing this fix.
I really appreciate your support and the time you take to help the community.

Your work on Traccar is amazing — thank you again!