Raspberry Pi作为MQTT出版商和订户

Question

我正在尝试同时建立RPI为发布者和订户。我将以这样的方式这样做，以便将subscriber.py和publisher.py作为线程，然后彼此运行。 当涉及到代码时，我遵循 https：// iotbytes。 wordpress.com/mosquitto-mqtt-broker-on-raspberry-pi/ 我也从这里拿了代码。首先，我在没有任何线程的情况下运行两个代码。 Publisher.py工作正常。 当我运行subscriber.py时，我会得到以下内容：

Traceback (most recent call last):
  File "/home/pi/subscriber.py", line 34, in <module>
    mqttc.loop_forever()
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 1756, in loop_forever
    rc = self._loop(timeout)
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 1164, in _loop
    rc = self.loop_read()
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 1556, in loop_read    rc = self._packet_read()
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 2439, in _packet_read
    rc = self._packet_handle()
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 3039, in _packet_handle
    return self._handle_connack()
  File "/home/pi/.local/lib/python3.9/site-packages/paho/mqtt/client.py", line 3138, in _handle_connack
    on_connect(
TypeError: on_connect() takes 3 positional arguments but 4 were given

这很奇怪，因为它不会放置4个参数。

代码：

import paho.mqtt.client as mqtt

# Define Variables
MQTT_BROKER = "test.mosquitto.org" # "192.168.0.13" #"MQTT Broker IP or DNS Name"
MQTT_PORT = 1883
MQTT_KEEPALIVE_INTERVAL = 45
MQTT_TOPIC = "testTopic"

# Define on_connect event Handler
def on_connect(mosq, obj, rc):
        #Subscribe to a the Topic
        mqttc.subscribe(MQTT_TOPIC, 0)

# Define on_subscribe event Handler
def on_subscribe(mosq, obj, mid, granted_qos):
    print ("Subscribed to MQTT Topic")

# Define on_message event Handler
def on_message(mosq, obj, msg):
        print (msg.payload)

# Initiate MQTT Client
mqttc = mqtt.Client()

# Register Event Handlers
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_subscribe = on_subscribe

# Connect with MQTT Broker
mqttc.connect(MQTT_BROKER, MQTT_PORT, MQTT_KEEPALIVE_INTERVAL)

# Continue the network loop
mqttc.loop_forever()

Answer 1

回调函数 on_connect 始终使用四个参数调用。 ，例如，eg 在这里

def on_connect(mqttc, obj, flags, rc):
    print("rc: " + str(rc))

这是不容易辨别的，因为函数调用发生在后台，并且您看不到调用函数的参数。

在您的代码中，您仅定义三个参数。这导致了令人困惑的错误消息。

即使您不使用它们，也需要使用四个参数来定义该函数。