Revert "Recall socket recv until get a complete response. (#143)" (#178)

This reverts commit 661c816.

Author: dhoomakethu

pymodbus/transaction.py

@@ -68,7 +68,7 @@ def _set_adu_size(self):
 
     def _calculate_response_length(self, expected_pdu_size):
         if self.base_adu_size == -1:
-            return None
+            return 1024
         else:
             return self.base_adu_size + expected_pdu_size
 
@@ -79,26 +79,21 @@ def execute(self, request):
         retries = self.retries
         request.transaction_id = self.getNextTID()
         _logger.debug("Running transaction %d" % request.transaction_id)
-
-        expected_response_length = None
         if hasattr(request, "get_response_pdu_size"):
             response_pdu_size = request.get_response_pdu_size()
-            if response_pdu_size:
-                expected_response_length = self._calculate_response_length(response_pdu_size)
+            expected_response_length = self._calculate_response_length(response_pdu_size)
+        else:
+            expected_response_length = 1024
 
         while retries > 0:
             try:
                 self.client.connect()
                 self.client._send(self.client.framer.buildPacket(request))
-
-                result = self.client._recv(expected_response_length or 1024)
-                while result and expected_response_length and len(result) < expected_response_length:
-                    result += self.client._recv(expected_response_length - len(result))
+                result = self.client._recv(expected_response_length)
 
                 if not result and self.retry_on_empty:
                     retries -= 1
                     continue
-
                 if _logger.isEnabledFor(logging.DEBUG):
                     _logger.debug("recv: " + " ".join([hex(byte2int(x)) for x in result]))
                 self.client.framer.processIncomingPacket(result, self.addTransaction)