python实现MQTT客户端通信的示例代码

import paho.mqtt.client as mqtt  
import time  
  
# MQTT服务器地址  
broker_address = "localhost"  # 替换为你的MQTT代理地址  
port = 1883  # MQTT代理的端口，默认为1883  
client_id = "python_mqtt_client"  # MQTT客户端的唯一ID  
topic = "test/topic"  # 要发布和订阅的主题  
username = "your_username"  # MQTT代理的用户名  
password = "your_password"  # MQTT代理的密码  
  
# 当连接到MQTT代理时调用的回调函数  
def on_connect(client, userdata, flags, rc):  
    print(f"Connected with result code {rc}")  
    # 订阅主题  
    client.subscribe(topic)  
  
# 当接收到MQTT消息时调用的回调函数  
def on_message(client, userdata, msg):  
    print(f"Received message '{msg.payload.decode('utf-8')}' on topic '{msg.topic}' with QoS {msg.qos}")  
  
# 创建MQTT客户端实例  
client = mqtt.Client(client_id)  
  
# 设置用户名和密码  
client.username_pw_set(username, password)  
  
# 为客户端设置回调函数  
client.on_connect = on_connect  
client.on_message = on_message  
  
# 连接到MQTT代理  
client.connect(broker_address, port)  
  
# 开始网络循环，处理接收到的消息和重连  
client.loop_start()  
  
try:  
    print("Publishing message...")  
    # 发布一条消息  
    client.publish(topic, "Hello, MQTT with username and password!", qos=1)  
      
    # 等待用户输入，以保持程序运行并接收消息  
    print("Press Enter to exit...")  
    input()  
except KeyboardInterrupt:  
    pass  
finally:  
    # 停止网络循环并断开连接  
    client.loop_stop()  
    client.disconnect()  
    print("Disconnected from MQTT broker.")