Prevent from sending more then one Modbus TCP response
for a single request.
This might happen in the following scenario where,
shortly after the first response has been sent (4),
the second one will be send (8) (note the same
'TransactionId') triggered by the response to the
'ModbusSend' request issued by Berry (5).
The log excerpt from such a situation:
(1) 21:13:20.510 MBS: MBRTCP to Modbus TransactionId:520, deviceAddress:4, functionCode:3, startAddress:8193, count:1, recvCount:1, recvBytes:2
(2) 21:13:20.523 MBS: Serial Send: 04 03 20 01 00 01 DE 5F
(3) 21:13:20.647 MBS: Serial Received: 04 03 02 0A 28 72 FA
(4) 21:13:20.652 MBS: MBRTCP from Modbus TransactionId:520, deviceAddress:4, writing:11 bytes to client (error:0)
(5) 21:13:20.724 CMD: Grp 0, Cmd 'MODBUSSEND', Idx 1, Len 89, Pld -99, Data '{"deviceAddress":4, "functionCode":6, "startAddress":8192, "type":"uint16", "Values":[6]}'
(6) 21:13:20.743 MBS: Serial Send: 04 06 20 00 00 06 02 5D
(7) 21:13:21.009 MBS: Serial Received: 04 06 20 00 00 06 02 5D
(8) 21:13:21.014 MBS: MBRTCP from Modbus TransactionId:520, deviceAddress:4, writing:12 bytes to client (error:0)
Use 'tcp_transaction_id' field to denote that we already
sent a response.
Signed-off-by: Damian Wrobel <dwrobel@ertelnet.rybnik.pl>
bf0f7316b9