mqtt python的写法

MQTT (Message Queuing Telemetry Transport) 是一种轻量级的发布/订阅消息协议，常用于物联网(IoT)应用中。在Python中使用Paho-MQTT库可以方便地操作MQTT。以下是简单的Paho-MQTT客户端连接、订阅和发布消息的基本步骤：

1. 首先，你需要安装paho-mqtt库。如果还没有安装，可以使用pip安装：

pip install paho-mqtt

2. 连接到MQTT服务器：

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print("Connected to MQTT broker")
    else:
        print(f"Connection failed with result code {rc}")

client = mqtt.Client()
client.on_connect = on_connect
client.connect("your_broker_address", port=1883, keepalive=60)

# 保持循环，以便及时处理来自服务器的消息
client.loop_forever()

3. 订阅主题：

def on_message(client, userdata, msg):
    print(f"Received message on topic '{msg.topic}': {str(msg.payload)}")

client.subscribe("your_topic")
client.on_message = on_message

4. 发布消息：

def publish_message(topic, payload):
    client.publish(topic, payload)
    
publish_message("another_topic", "Hello World!")

5. 关闭连接：

def on_disconnect(client, userdata, rc):
    print("Disconnected from MQTT broker")
    client.disconnect()

client.on_disconnect = on_disconnect
# 等待断开连接或者手动调用client.disconnect()关闭连接