Question

我在Raspberry Pi上有一个简单的脚本，它每3秒发布一条示例消息。我已经声明了回调on_connect，on_publish和on_disconnect。此客户端连接成功，但未调用on_connect，调用发布和on_publish，调用disconnectcts和on_disconnect。

这是我的剧本

import paho.mqtt.client as mqtt
import time

def on_connect(mqttc, userdata, rc):
    print("Connected with result code "+str(rc))
    if rc!=0 :
        mqttc.reconnect()

def on_publish(mqttc, userdata, mid):
    print "Published"

def on_disconnect(mqttc, userdata, rc):
    if rc != 0:
        print("Unexpected disconnection. Reconnecting...")
        mqttc.reconnect()
    else :
        print "Disconnected successfully"

# Setup MQTT
# broker='test.mosquitto.org'
broker = 'iot.eclipse.org'
broker_port=1883

# Create a client instance
mqttc=mqtt.Client(client_id="MyClient")
mqttc.on_connect = on_connect
mqttc.on_publish = on_publish
mqttc.on_disconnect = on_disconnect

while 1:

    mqttc.connect(broker, broker_port, 60)
    # print "Connected."    # I don't want this message. 
                            # Why isn't the on_connect callback invoked?

    try:
        topic = "this/is/a/test/topic"
        payload = "test_message"
        print "Publishing " + payload + " to topic: " + topic + " ..."
        mqttc.publish(topic, payload, 0)

    except Exception as e:
        print "exception"
        log_file=open("log.txt","w")
        log_file.write(str(time.time())+" "+e.__str__())
        log_file.close()

    mqttc.disconnect()
    print ""
    time.sleep(3)

虽然这个小故障＆＃34; bug＆＃34;不会影响消息发布，这主要是我想要实现的，为什么会发生，我该如何解决呢？

Answer 1

这不起作用的原因是你没有调用任何loop*()函数。这些处理网络流量。如果您不使用，则无法保证您的外发消息将被发送，并且绝对不会处理任何传入消息。

loop_forever()是一个阻止调用来处理网络循环 - 可能不是你想要的。

loop_start()启动一个线程来处理网络循环，因此立即返回。

我会这样做：

mqttc.connect(broker, broker_port, 60) # Don't forget to handle errors
mqttc.loop_start()

while 1:
    try:
        topic = "this/is/a/test/topic"
        payload = "test_message"
        print "Publishing " + payload + " to topic: " + topic + " ..."
        mqttc.publish(topic, payload, 0)

    except Exception as e:
        print "exception"
        log_file=open("log.txt","w")
        log_file.write(str(time.time())+" "+e.__str__())
        log_file.close()

    print ""
    time.sleep(3)

你仍然需要修复你的on_connect回调，因为@Kiran说。

每次都不需要断开连接 - 事实上，当您断开连接时，无法保证您的消息将被发送。您应该使用on_publish回调来了解邮件的发送时间。

如果你想做一个简单的connect-publish-disconnect，那么可以使用paho.mqtt.publish助手模块：

import paho.mqtt.publish as publish

while 1:
    try:
        topic = "this/is/a/test/topic"
        payload = "test_message"
        print "Publishing " + payload + " to topic: " + topic + " ..."
        publish.single(topic, payload, 0, host=broker, port=broker_port)

    except Exception as e:
        print "exception"
        log_file=open("log.txt","w")
        log_file.write(str(time.time())+" "+e.__str__())
        log_file.close()

    print ""
    time.sleep(3)

Answer 2

您的on_connect()方法声明缺少标记（1）参数。所以它没有被调用。 Flags参数包含代理发送的响应。它必须是

def on_connect(mqttc, userdata, flags, rc):

另外，为什么要在循环中连接和断开连接？尝试使用loop_start()和loop_stop()方法处理连接丢弃（example）上的自动重新连接。

Paho Python MQTT客户端连接成功，但未调用on_connect回调

2 个答案: