为什么我的 Python MQTT 发布者没有发布任何内容答案

【问题标题】：Why isnt my Python MQTT publisher publish anything out为什么我的 Python MQTT 发布者没有发布任何内容
【发布时间】：2017-01-18 07:43:20
【问题描述】：

我正在为与 MQTT 集成的项目运行交通灯 (pi-stop) 解决方案。因此，发布者将计数发送给订阅者，订阅者将控制和更改交通信号灯。但是，我无法将任何计数发送给出版商。请指教，谢谢

MQTT_pub.py（发布者）

import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish

sub_topic = "light" #recieve message on this topic

pub_topic = "light" #send message to this topic

Broker = "127.0.1.1" 

# when connecting to mqtt do this;

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe(sub_topic)

# when receiving a mqtt message do this;

def on_message(client, userdata, msg):
    message = str(msg.payload)
    print(msg.topic+" "+message)
    # publish_mqtt("got your message")

# to send a message

def publish_mqtt(count):
    mqttc = mqtt.Client("counting")
    mqttc.connect(Broker, 1883)
    mqttc.publish(pub_topic, "10")
    #mqttc.loop(5) //timeout = 5s

def on_publish(mosq, obj, mid):
    print("mid: " + str(mid))

client = mqtt.Client()

client.on_connect = on_connect
client.on_message = on_message

client.connect(Broker, 1883, 60)
publish_mqtt(0)

MQTT.py（订阅者）

import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
import TrafficKit03

sub_topic = "light" #recieve message on this topic

pub_topic = "light" #send message to this topic

Broker = "127.0.0.1" 


# when connecting to mqtt do this;

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe(sub_topic)

# when receiving a mqtt message do this;

def on_message(client, userdata, msg):
    message = str(msg.payload)
    print(msg.topic+" "+message)
    # decide on traffic counting (if 5 display.. if 0 display..)
    publish_mqtt(count)
    TrafficKit03.call("TrafficKit03.py")


def on_subscribe(client, userdata, mid, gqos):
    print("subscribed: " + gpos)
    pass


 def publish_mqtt(count):
    mqttc = mqtt.Client("counting")
    mqttc.connect(Broker, 1883)
    mqttc.publish(pub_topic, "10")
    #mqttc.loop(5) //timeout = 5s

client = mqtt.Client()

client.on_connect = on_connect
client.on_subscribe = on_subscribe
client.on_message = on_message


client.connect(Broker, 1883, 60)
client.loop_start()

【问题讨论】：

我之前没有使用过 Python 的 MQTT，但是你应该在 publisher.py 中创建两个 mqtt.Client() 的实例吗？
@Tagc 抱歉，我不太确定。

标签： python mqtt publisher

【解决方案1】：

正如@Tagic 所说，您需要删除额外的mqtt.Client() 实例

编辑这两个文件以删除publish_mqtt 函数中的额外连接

def publish_mqtt(count):
    #mqttc = mqtt.Client("counting")
    #mqttc.connect(Broker, 1883)
    mqttc.publish(pub_topic, "10")
    #mqttc.loop(5) //timeout = 5s

在 MQTT_pub.py 文件中，您还应该将对 publish_mqtt 的调用移至 on_connect 函数：

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    publish_mqtt(0)

并启动网络循环

client.connect(Broker, 1883, 60)
client.loop_start()

【讨论】：