python3 使用paho-mqtt

python版本：python3.8

mqtt库：paho-mqtt 1.6.1

 

一，消息发布

创建pub.py，写入以下代码

import time
from paho.mqtt import client as mqtt_client


# broker服务器，远程中间人的主机或IP
broker = 'localhost'
# 端口，默认端口是1883
port = 1883
# 主题（要和订阅端保持一致）
topic = 'topic1'
# 客户端id（随机字符串）
client_id = '001'

def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print("Connected to MQTT Broker!")
    else:
        print(f"Failed to connect, return code {rc}")

def conn_mqtt():
    client = mqtt_client.Client(client_id)
    client.on_connect = on_connect
    client.connect(broker, port)
    return client

def publish(client):
    msg_count = 0
    while True:
        time.sleep(1)
        msg = f"msg of {msg_count}!"
        res = client.publish(topic=topic, payload=msg, qos=1)
        if res[0] == 0:
            print(f"send {msg} successful!")
        else:
            print("Fail to send msg!")
        msg_count += 1

if __name__ == "__main__":
    client = conn_mqtt()
    publish(client)

 

二，消息接收（消息订阅）

创建文件sub.py，写入以下代码

from paho.mqtt import client as mqtt_client


broker = 'localhost'
port = 1883
topic = 'topic1'
client_id = '002'


def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print("Connected to MQTT Broker!")
    else:
        print(f"Failed to connect, return code {rc}")

def conn_mqtt():
    client = mqtt_client.Client(client_id)
    client.on_connect = on_connect
    client.connect(broker, port)
    return client

def on_message(client, userdata, msg):
    print(f"Received {msg.payload.decode()}!")

def subscribe(client):
    client.subscribe(topic=topic, qos=1)
    client.on_message = on_message
    client.loop_forever()

if __name__ == "__main__":
    client = conn_mqtt()
    subscribe(client)

 注意：qos参数值说明

qos=0，最多发送一次。

qos=1，最少发送一次

qos=2，只发送一次，并且一定能送到

 

三，启动

 

四，MQTT连接错误码

rc=0：连接成功

rc=1：协议版本不接受

rc=2：无效客户端标识符被拒绝

rc=3：服务不可用

rc=4：用户名或密码错误

rc=5：无权连接