I'm trying to get a basic python paho client to work. Unfortunately paho keeps crashing on different errors instead of handling the mqtt messages.
python client code (mostly taken from the python paho doc):
from paho.mqtt import client as mqtt_client
broker = '127.0.0.1'
port = 1883
topic = "home/sensors/dht22"
client_id = f'python-mqtt-dht22'
PASSWORD = "password"
def connect_mqtt():
def on_connect(client, userdata, flags, rc):
if rc == 0:
print("Connected to MQTT Broker!")
else:
print("Failed to connect, return code %d\n", rc)
client = mqtt_client.Client(mqtt_client.CallbackAPIVersion.VERSION1, client_id)
client.username_pw_set("simon", PASSWORD)
client.on_connect = on_connect
client.connect(broker, port)
return client
def subscribe(client: mqtt_client):
def on_message(client, userdata, msg):
payload = msg.payload.decode()
print(f"Received `{payload}` from `{msg.topic}` topic")
handle_msg(payload)
client.subscribe(topic)
client.on_message = on_message
def run():
client = connect_mqtt()
client.loop_start()
subscribe(client)
client.loop_forever()
if __name__ == '__main__':
run()
Running this together with mosquitto nondeterministically results in either
Exception in thread paho-mqtt-client-python-mqtt-dht22:
Traceback (most recent call last):
File "/usr/lib/python3.12/threading.py", line 1073, in _bootstrap_inner
self.run()
File "/usr/lib/python3.12/threading.py", line 1010, in run
self._target(*self._args, **self._kwargs)
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 4523, in _thread_main
self.loop_forever(retry_first_connection=True)
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2297, in loop_forever
rc = self._loop(timeout)
^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 1686, in _loop
rc = self.loop_read()
^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2100, in loop_read
rc = self._packet_read()
^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3142, in _packet_read
rc = self._packet_handle()
^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3808, in _packet_handle
return self._handle_publish()
^^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 4099, in _handle_publish
(slen, packet) = struct.unpack(pack_format, self._in_packet['packet'])
struct.error: bad char in struct format
or in
Exception in thread paho-mqtt-client-python-mqtt-dht22:
Traceback (most recent call last):
File "/usr/lib/python3.12/threading.py", line 1073, in _bootstrap_inner
Traceback (most recent call last):
File "/home/simon/code/mqtt_sink.py", line 76, in <module>
self.run()
File "/usr/lib/python3.12/threading.py", line 1010, in run
self._target(*self._args, **self._kwargs)
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 4523, in _thread_main
run()
self.loop_forever(retry_first_connection=True)
File "/home/simon/code/mqtt_sink.py", line 71, in run
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2297, in loop_forever
client.loop_forever()
rc = self._loop(timeout)
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2297, in loop_forever
^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 1686, in _loop
rc = self._loop(timeout)
^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 1686, in _loop
rc = self.loop_read()
rc = self.loop_read()
^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2100, in loop_read
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 2100, in loop_read
rc = self._packet_read()
rc = self._packet_read()
^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3142, in _packet_read
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3142, in _packet_read
rc = self._packet_handle()
rc = self._packet_handle()
^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3816, in _packet_handle
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 3816, in _packet_handle
self._handle_suback()
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 4053, in _handle_suback
self._handle_suback()
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/client.py", line 4053, in _handle_suback
reasoncodes = [ReasonCode(SUBACK >> 4, identifier=c) for c in granted_qos]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 129, in __init__
reasoncodes = [ReasonCode(SUBACK >> 4, identifier=c) for c in granted_qos]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 129, in __init__
self.getName() # check it's good
self.getName() # check it's good
^^^^^^^^^^^^^^
^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 172, in getName
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 172, in getName
return self.__getName__(self.packetType, self.value)
return self.__getName__(self.packetType, self.value)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 140, in __getName__
File "/home/simon/.avenv/mqtt/lib/python3.12/site-packages/paho/mqtt/reasoncodes.py", line 140, in __getName__
raise KeyError(identifier)
raise KeyError(identifier)
KeyError: 48
Either way it doesn't work. I've searched a bit, but haven't found anything useful on the internet, yet.
The mosquitto server and the message source work, as
mosquitto_sub -u simon -P password -t "home/sensors/dht22" -i spy displays the sent messages.
What is wrong with my code, any ideas?
EDIT 2024-11-13:
I've managed to get it to work by removing client.loop_start(). So if you have similar problems: use loop_forever().
def run():
client = connect_mqtt()
client.loop_start()
subscribe(client)
client.loop_forever()
You are starting two network loops (one with loop_start() and a second with loop_forever()). This will cause issues like the ones you are seeing because two processes will be attempting to process the data received from the broker (and there will be data races).
Removing the client.loop_start() should fix this. I would also suggest that you move the subscribe into on_connect (as per the examples).