#221 Fix read transactions for different framers

Author: dhoomakethu

pymodbus/server/sync.py

@@ -101,10 +101,12 @@ def handle(self):
                 data = self.request.recv(1024)
                 if data:
                     if _logger.isEnabledFor(logging.DEBUG):
-                        _logger.debug(" ".join([hex(byte2int(x)) for x in data]))
-                    if not isinstance(self.framer, ModbusBinaryFramer):
+                        _logger.debug("recv: " + " ".join([hex(byte2int(x)) for x in data]))
+                    if isinstance(self.framer, ModbusRtuFramer):
                         unit_address = byte2int(data[0])
-                    else:
+                    elif isinstance(self.framer, ModbusAsciiFramer):
+                        unit_address = int(data[1:3], 16)
+                    if isinstance(self.framer, ModbusBinaryFramer):
                         unit_address = byte2int(data[1])
                     if unit_address in self.server.context:
                         self.framer.processIncomingPacket(data, self.execute)
@@ -114,6 +116,7 @@ def handle(self):
                 self.framer.resetFrame()
                 _logger.error("Socket error occurred %s" % msg)
 
+
     def send(self, message):
         ''' Send a request (string) to the network
 

pymodbus/transaction.py

@@ -5,7 +5,7 @@
 import struct
 import socket
 from binascii import b2a_hex, a2b_hex
-
+from serial import SerialException
 from pymodbus.exceptions import ModbusIOException, NotImplementedException
 from pymodbus.exceptions import InvalidMessageRecievedException
 from pymodbus.constants  import Defaults
@@ -57,13 +57,13 @@ def __init__(self, client, **kwargs):
     def _set_adu_size(self):
         # base ADU size of modbus frame in bytes
         if isinstance(self.client.framer, ModbusSocketFramer):
-            self.base_adu_size = 7 # tid(2), pid(2), length(2), uid(1)
+            self.base_adu_size = 7  # tid(2), pid(2), length(2), uid(1)
         elif isinstance(self.client.framer, ModbusRtuFramer):
-            self.base_adu_size = 3 # address(1), CRC(2)
+            self.base_adu_size = 3  # address(1), CRC(2)
         elif isinstance(self.client.framer, ModbusAsciiFramer):
-            self.base_adu_size = 7 # start(1)+ Address(2), LRC(2) + end(2)
+            self.base_adu_size = 7  # start(1)+ Address(2), LRC(2) + end(2)
         elif isinstance(self.client.framer, ModbusBinaryFramer):
-            self.base_adu_size = 3 #, Address(1), CRC(2)
+            self.base_adu_size = 5  # start(1) + Address(1), CRC(2) + end(1)
         else:
             self.base_adu_size = -1
 
@@ -169,20 +169,35 @@ def _recv(self, expected_response_length):
                     expected_response_length = self._calculate_exception_length()
                     continue
                 if isinstance(self.client.framer, ModbusSocketFramer):
-                    length = struct.unpack(">H", result[4:6])[0] -1  # Ommit UID, which is included in header size
-                    expected_response_length = self.client.framer._ModbusSocketFramer__hsize + length
-
-                r = self.client._recv(expected_response_length - len(result))
-                if not r:
-                    # If no response being recived there is no point in conitnuing
+                    # Ommit UID, which is included in header size
+                    h_size = self.client.framer._ModbusSocketFramer__hsize
+                    length = struct.unpack(">H", result[4:6])[0] -1
+                    expected_response_length = h_size + length
+
+                if expected_response_length != len(result):
+                    _logger.debug("Expected - {} bytes, "
+                                  "Actual - {} bytes".format(
+                        expected_response_length, len(result))
+                    )
+                    try:
+                        r = self.client._recv(
+                            expected_response_length - len(result)
+                        )
+                        result += r
+                        if not r:
+                            # If no response being recived there
+                            # is no point in conitnuing
+                            break
+                    except (TimeoutError, SerialException):
+                        break
+                else:
                     break
-                result += r
+
             if result:
                 break
             retries -= 1
         return result
 
-
     def addTransaction(self, request, tid=None):
         ''' Adds a transaction to the handler
 

requirements.txt

@@ -1,3 +1,4 @@
+six==1.11.0
 # -------------------------------------------------------------------
 # if want to use the pymodbus serial stack, uncomment these
 # -------------------------------------------------------------------