python链接mqtt订阅与发布

什么是mqtt：

MQTT 全称为 Message Queuing Telemetry Transport（消息队列遥测传输）是一种基于发布/订阅范式的“轻量级”消息协议。该协议构建于TCP/IP协议上

MQTT三种服务：

“至多一次”，消息发布完全依赖底层 TCP/IP 网络。会发生消息丢失或重复。这一级别可用于如下情况，环境传感器数据，丢失一次读记录无所谓，因为不久后还会有第二次发送。
“至少一次”，确保消息到达，但消息重复可能会发生。
“只有一次”，确保消息到达一次。这一级别可用于如下情况，在计费系统中，消息重复或丢失会导致不正确的结果。

用python实现发布、订阅：

安装：pip install paho-mqtt 如何安装失败，可以尝试换豆瓣源pip install paho-mqtt -i https://pypi.douban.com/simple/

订阅：

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import random   from paho.mqtt import client as mqtt_client     broker = #ip地址 port = 1883 topic = "/python/mqtt" # generate client ID with pub prefix randomly client_id = #client_id     def connect_mqtt() -> mqtt_client:     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(client_id)     client.on_connect = on_connect     client.connect(broker, port)     return client     def subscribe(client: mqtt_client):     def on_message(client, userdata, msg):         print(f"Received `{msg.payload.decode()}` from `{msg.topic}` topic")       client.subscribe(topic)     client.on_message = on_message     def run():     client = connect_mqtt()     subscribe(client)     client.loop_forever()     if __name__ == '__main__':     run()

 消息发布

 

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import random import time   from paho.mqtt import client as mqtt_client #基本链接数据同上 topic="" def clicent_main(client,message: str):     """     客户端发布消息     :param message: 消息主体     :return:     """     time_now = time.strftime('%Y-%m-%d %H-%M-%S', time.localtime(time.time()))     payload = {"msg": "%s" % message, "data": "%s" % time_now}     # publish(主题：Topic; 消息内容)     client.publish(topic, json.dumps(payload, ensure_ascii=False))     print("Successful send message!")     return True