Incomplete message received, Expected 9 bytes Recieved 8 bytes on pymodbus 2.5.3

[mehtajaimin]

Hi,
I am using pymodbus 2.5.3 and trying to communicate with a modbus device. The device responds correctly as seen in a serial sniffer but on Pymodbus the response misses the first two bytes and we see a 0x0 in place of the first two bytes of the frame. This leads to a processing error.Here are some logs:

2023-12-11 04:17:50,331 ModbusRTUClient DEBUG transaction :369 Incomplete message received, Expected 9 bytes Recieved 8 bytes !!!!
2023-12-11 04:17:50,332 ModbusRTUClient DEBUG transaction :375 Changing transaction state from 'WAITING FOR REPLY' to 'PROCESSING REPLY'
2023-12-11 04:17:50,333 ModbusRTUClient DEBUG transaction :297 RECV: 0x0 0x4 0x0 0x88 0x30 0x47 0x1d 0x2b
2023-12-11 04:17:50,348 ModbusRTUClient DEBUG rtu_framer :237 Frame check failed, ignoring!!
2023-12-11 04:17:50,361 ModbusRTUClient DEBUG rtu_framer :120 Resetting frame - Current Frame in buffer - 0x0 0x4 0x0 0x88 0x30 0x47 0x1d 0x2b
2023-12-11 04:17:50,379 ModbusRTUClient DEBUG transaction :465 Getting transaction 2
2023-12-11 04:17:50,399 ModbusRTUClient DEBUG transaction :224 Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'
2023-12-11 04:17:50,503 WebSocketClient DEBUG protocol :253 = connection is CONNECTING
2023-12-11 04:17:50,524 ModbusRTUClient DEBUG transaction :140 Current transaction state - TRANSACTION_COMPLETE
2023-12-11 04:17:50,544 ModbusRTUClient DEBUG transaction :145 Running transaction 3
2023-12-11 04:17:50,562 ModbusRTUClient DEBUG transaction :273 SEND: 0x1 0x3 0x0 0x0 0x0 0x2 0xc4 0xb
2023-12-11 04:17:53,649 ModbusRTUClient DEBUG transaction :369 Incomplete message received, Expected 9 bytes Recieved 8 bytes !!!!
2023-12-11 04:17:53,650 ModbusRTUClient DEBUG transaction :375 Changing transaction state from 'WAITING FOR REPLY' to 'PROCESSING REPLY'
2023-12-11 04:17:53,652 ModbusRTUClient DEBUG transaction :297 RECV: 0x0 0x4 0x0 0x88 0x30 0x47 0x2e 0x2b
2023-12-11 04:17:53,666 ModbusRTUClient DEBUG rtu_framer :237 Frame check failed, ignoring!!
2023-12-11 04:17:53,682 ModbusRTUClient DEBUG rtu_framer :120 Resetting frame - Current Frame in buffer - 0x0 0x4 0x0 0x88 0x30 0x47 0x2e 0x2b
2023-12-11 04:17:53,697 ModbusRTUClient DEBUG transaction :465 Getting transaction 1
2023-12-11 04:17:53,721 ModbusRTUClient DEBUG transaction :224 Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'
2023-12-11 04:17:53,843 ModbusRTUClient DEBUG transaction :140 Current transaction state - TRANSACTION_COMPLETE

I am not able to determine how to overcome this loss of the first two bytes. The rest of the frame is ok.

Any help is greatly appreciated.

[janiversen]

You probably have a wrong framer.

We no longer support v2.5.3 so please update to newest version.