Do not filter using unit id in the received response (#1076)

processIncomingPacket() can be told to ignore unit ids other than the
specified one or accept all packets by specifying id 0 or 0xff. The
modbus client would extract the unit id from the incoming data packet
and use that for filtering. At best this is a no-op: the incoming unit
id will match itself. At worst it makes us drop responses: if the data
is fragmented each fragment was incorrectly parsed to extract a unit
id.

Remove the incoming unit id check at this stage. This change is
behavior preserving if the response is not fragmented and fixes
riptideio#688 if it is fragmented.

Author: JonasNorling

pymodbus/client/base.py

@@ -380,8 +380,7 @@ def _data_received(self, data):
         """Get response, check for valid message, decode result."""
         txt = f"recv: {hexlify_packets(data)}"
         _logger.debug(txt)
-        unit = self.framer.decode_data(data).get("unit", 0)
-        self.framer.processIncomingPacket(data, self._handle_response, unit=unit)
+        self.framer.processIncomingPacket(data, self._handle_response, unit=0)
 
     def _handle_response(self, reply, **kwargs):  # pylint: disable=unused-argument
         """Handle the processed response and link to correct deferred."""