Merge pull request #297 from aws/SocketReadFix

Apply socket read fix from public gihub issue #296

Author: bretambrose

AWSIoTPythonSDK/core/protocol/paho/client.py

@@ -877,6 +877,15 @@ def loop(self, timeout=1.0, max_packets=1):
         self._out_packet_mutex.release()
         self._current_out_packet_mutex.release()
 
+        # used to check if there are any bytes left in the ssl socket
+        pending_bytes = 0
+        if self._ssl:
+            pending_bytes = self._ssl.pending()
+
+        # if bytes are pending do not wait in select
+        if pending_bytes > 0:
+            timeout = 0.0
+
         # sockpairR is used to break out of select() before the timeout, on a
         # call to publish() etc.
         rlist = [self.socket(), self._sockpairR]
@@ -892,7 +901,7 @@ def loop(self, timeout=1.0, max_packets=1):
         except:
             return MQTT_ERR_UNKNOWN
 
-        if self.socket() in socklist[0]:
+        if self.socket() in socklist[0] or pending_bytes > 0:
             rc = self.loop_read(max_packets)
             if rc or (self._ssl is None and self._sock is None):
                 return rc