WIP
This commit is contained in:
Vladimir Vukicevic
186
simple_mqtt_server.py
Normal file
186
simple_mqtt_server.py
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import asyncio
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import struct
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MQTT_CONNECT = 1
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MQTT_CONNACK = 2
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MQTT_PUBLISH = 3
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MQTT_PUBACK = 4
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MQTT_SUBSCRIBE = 8
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MQTT_SUBACK = 9
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MQTT_DISCONNECT = 14
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class SimpleMQTTServer:
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def __init__(self, host, port):
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self.host = host
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self.port = port
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self.server = None
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self.incoming_messages = asyncio.Queue()
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self.outgoing_messages = asyncio.Queue()
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self.next_pack_id_value = 1
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async def start(self):
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self.server = await asyncio.start_server(self.handle_client, self.host, self.port)
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self.port = self.server.sockets[0].getsockname()[1]
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print(f'Listening on {self.server.sockets[0].getsockname()}')
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async def serve_forever(self):
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await self.server.serve_forever()
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async def handle_client(self, reader, writer):
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addr = writer.get_extra_info('peername')
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print(f'Socket connected from {addr}')
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data = b''
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read_future = asyncio.ensure_future(reader.read(1024))
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outgoing_messages_future = asyncio.ensure_future(self.outgoing_messages.get())
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subscribed_topics = dict()
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while True:
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# get Future representing a reader.read(1024)
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# get Future representing a self.incoming_messages.get()
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completed, pending = await asyncio.wait([read_future, outgoing_messages_future], return_when=asyncio.FIRST_COMPLETED)
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#print(completed)
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#print(pending)
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if outgoing_messages_future in completed:
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#print("Got outgoing message")
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outmsg = outgoing_messages_future.result()
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topic = outmsg['topic']
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payload = outmsg['payload']
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if topic in subscribed_topics:
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qos = subscribed_topics[topic]
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await self.send_msg(writer, MQTT_PUBLISH, payload=self.encode_publish(topic, payload, self.next_pack_id()))
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else:
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print(f'SEND: NOT SUBSCRIBED {topic}: {payload}')
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#msg = (MQTT_PUBLISH, 0, topic.encode('utf-8') + payload.encode('utf-8'))
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#await self.send_msg(writer, *msg)
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outgoing_messages_future = asyncio.ensure_future(self.outgoing_messages.get())
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if read_future in completed:
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d = read_future.result()
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data += d
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read_future = asyncio.ensure_future(reader.read(1024))
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else:
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continue
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# Process any messages
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while True:
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# must have at least 2 bytes
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if len(data) < 2:
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break
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#print(f"Remaining bytes: {len(data)}")
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#print(f"Data: {data}")
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msg_type = data[0] >> 4
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msg_flags = data[0] & 0xf
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#print(f" msg_type: {msg_type} msg_flags: {msg_flags}")
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# TODO -- we could maybe not have enough bytes to decode the length, but assume
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# that won't happen
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msg_length, len_bytes_consumed = self.decode_length(data[1:])
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print(f" in msg_type: {msg_type} flags: {msg_flags} msg_length {msg_length} bytes_consumed for msg_length {len_bytes_consumed}")
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# is there enough to process the message?
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head_len = len_bytes_consumed + 1
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if msg_length + head_len > len(data):
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print("Not enough")
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break
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# pull the message payload out, and move data to next packet
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message = data[head_len :head_len+msg_length]
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data = data[head_len+msg_length:]
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if msg_type == MQTT_CONNECT:
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# ignore the contents of the message, should maybe check for 'MQTT' identifier at least
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print(f"Client {addr} connected")
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await self.send_msg(writer, MQTT_CONNACK, payload=b'\x00\x00')
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elif msg_type == MQTT_PUBLISH:
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qos = (msg_flags >> 1) & 0x3
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topic, packid, content = self.parse_publish(message)
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print(f"{topic}: {content}")
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if qos > 0:
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await self.send_msg(writer, MQTT_PUBACK, packet_ident=packid)
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elif msg_type == MQTT_SUBSCRIBE:
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qos = (msg_flags >> 1) & 0x3
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packid = message[0] << 8 | message[1]
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message = message[2:]
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topic = self.parse_subscribe(message)
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print(f"Client {addr} subscribed to topic '{topic}', QoS {qos}")
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subscribed_topics[topic] = qos
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await self.send_msg(writer, MQTT_SUBACK, packet_ident=packid, payload=bytes([qos]))
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elif msg_type == MQTT_DISCONNECT:
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print(f"Client {addr} disconnected")
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writer.close()
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await writer.wait_closed()
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return
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async def send_msg(self, writer, msg_type, flags=0, packet_ident=0, payload=b''):
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head = bytes([msg_type << 4 | flags])
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payload_length = len(payload)
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if packet_ident > 0:
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payload_length += 2
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head += self.encode_length(payload_length)
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if packet_ident > 0:
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head += bytes([packet_ident >> 8, packet_ident & 0xff])
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data = head + payload
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print(f" writing {len(data)} bytes: {data}")
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writer.write(data)
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await writer.drain()
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def encode_length(self, length):
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encoded = bytearray()
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while True:
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digit = length % 128
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length //= 128
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if length > 0:
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digit |= 0x80
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encoded.append(digit)
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if length == 0:
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break
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return encoded
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def decode_length(self, data):
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multiplier = 1
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value = 0
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bytes_read = 0
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for byte in data:
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bytes_read += 1
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value += (byte & 0x7f) * multiplier
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if byte & 0x80 == 0:
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break
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multiplier *= 128
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if multiplier > 2097152:
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raise ValueError("Malformed Remaining Length")
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return value, bytes_read
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def parse_publish(self, data):
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topic_len = struct.unpack("!H", data[0:2])[0]
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topic = data[2:2 + topic_len].decode("utf-8")
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packid = struct.unpack("!H", data[2 + topic_len:4 + topic_len])[0]
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message_start = 4 + topic_len
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message = data[message_start:].decode("utf-8")
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return topic, packid, message
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def parse_subscribe(self, data):
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topic_len = struct.unpack("!H", data[0:2])[0]
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topic = data[2:2 + topic_len].decode("utf-8")
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return topic
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def encode_publish(self, topic, message, packid=0):
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topic_len = len(topic)
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topic = topic.encode("utf-8")
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packid = struct.pack("!H", packid)
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message = message.encode("utf-8")
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return struct.pack("!H", topic_len) + topic + packid + message
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def next_pack_id(self):
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pack_id = self.next_pack_id_value
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self.next_pack_id_value += 1
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return pack_id
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if __name__ == "__main__":
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server = SimpleMQTTServer()
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asyncio.run(server.run())
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