MQTT的发布和订阅

准备工作

本文测试MQTT的发布/订阅，分为客户端版和python版。

首先我们需要一个MQTT服务器，这里推荐使用EMQ，一步搭建，省去了很多部署的麻烦。

选择Windows版本下载，自己选择目录解压后，进入bin目录打开cmd，运行emqx start命令开启服务即可。此时在浏览器地址栏输入: localhost:18083，输入用户名：admin，密码：public进入，可以看到主界面。

Python版本

下载库

cmd下执行这个命令

1	pip install paho-mqtt

编写订阅端

新建一个mqtt_sub.py文件，编写代码如下：

import paho.mqtt.client as mqtt

HOST = "127.0.0.1"
PORT = 1883


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


def on_message(client, userdata, msg):
    print(msg.topic + " " + ":" + str(msg.payload))


client = mqtt.Client()
client.on_connect = on_connect
client.on_message = on_message
client.connect(host=HOST, port=PORT, keepalive=600)
client.loop_forever()

编写发布端

新建一个mqtt_pub.py文件，编写代码如下：

import paho.mqtt.client as mqtt

HOST = "127.0.0.1"
PORT = 1883
mqttClient = mqtt.Client()


# 连接MQTT服务器
def on_mqtt_connect():
    mqttClient.connect(host=HOST, port=PORT, keepalive=600)
    mqttClient.loop_start()


# publish 消息
def on_publish(topic, payload, qos):
    mqttClient.publish(topic, payload, qos)


# 消息处理函数
def on_message_come(client, userdata, msg):
    print(msg.topic + " " + ":" + str(msg.payload))


# subscribe 消息
def on_subscribe():
    mqttClient.subscribe(topic="chat", qos=2)
    mqttClient.on_message = on_message_come  # 消息到来处理函数


def main():
    on_mqtt_connect()
    on_publish(topic="chat", payload="Hello Python!", qos=2)
    on_subscribe()
    while True:
        pass


if __name__ == '__main__':
    main()