Check CONNECT is the first message received and that it is received only once

hbmqtt/broker.py

@@ -10,6 +10,7 @@ from hbmqtt.codecs.header import MQTTHeaderCodec
 from hbmqtt.codecs.errors import CodecException
 from hbmqtt.codecs.connect import ConnectMessage
 from hbmqtt.message import MessageType
+from hbmqtt.errors import MQTTException
 
 
 class BrokerProtocol(asyncio.Protocol):
@@ -100,13 +101,20 @@ def init_message_codecs():
 def client_connected(reader, writer):
     (remote_address, remote_port) = writer.get_extra_info('peername')
     codecs = init_message_codecs()
+    first_packet = True
     while True:
         try:
             # Read fixed header
-            fixed_header = yield from MQTTHeaderCodec.decode(reader)
+            header = yield from MQTTHeaderCodec.decode(reader)
+            if first_packet and header.message_type != MessageType.CONNECT:
+                raise MQTTException("[MQTT-3.1.0-1] First Packet sent from the Client MUST be a CONNECT Packet")
+            if not first_packet and header.message_type == MessageType.CONNECT:
+                raise MQTTException("[MQTT-3.1.0-2] Client can only send the CONNECT Packet once over a Network Connection")
+            first_packet = False
             # Find message decoder and decode
-            codec = codecs[fixed_header.message_type]
-            message = yield from codec.decode(fixed_header, reader)
-        except CodecException:
+            codec = codecs[header.message_type]
+            message = yield from codec.decode(header, reader)
+
+        except MQTTException:
             #End connection
             break