Python使用MQTT举例 | 烟雨平生

关于MQTT的简介和服务器的搭建，之前已经写了笔记了：Docker搭建MQTT服务器

用来学习、研究，自己不搭MQTT服务器也行，EMQX有提供免费的在线 MQTT 服务器（还提供证书的下载）：
官网：https://www.emqx.com/zh/mqtt/public-mqtt5-broker

MQTT 服务器信息
Broker: broker-cn.emqx.io
TCP 端口: 1883
WebSocket 端口: 8083
SSL/TLS 端口: 8883
WebSocket Secure 端口: 8084

Python使用MQTT的例子，主要就写2个python文件，一个用来publish（发布消息），一个用来subcribe（订阅消息），看看是不是都能接收到消息。（消息订阅后都能接收到，就可以存入自己建的本地数据库啦）

一、安装paho-mqtt库

1	pip install paho-mqtt

安装了这个库就可以处理MQTT了，官方文档上也例子：https://pypi.org/project/paho-mqtt/#

二、publish发布消息（mqtt_publish.py）

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
import paho.mqtt.client as mqtt_client
import time, json, random

# MQTT连接
def connect_mqtt():
    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)
    # Set Connecting Client ID
    client = mqtt_client.Client(client_id)
    client.on_connect = on_connect
    client.connect(broker, port)
    return client

# 发布消息
def publish(client, topic, msg):
    # msg = f"messages: {msg_count}"
    result = client.publish(topic, msg)
    # result: [0, 1]
    status = result[0]
    if status == 0:
        print(f"Send `{msg}` to topic `{topic}`")
    else:
        print(f"Failed to send message to topic {topic}")

def run_publish():
    client = connect_mqtt()
    time.sleep(1)
    client.loop_start()
    # 发布消息
    # stus = {"Tempeature":30.1,"Humidity":40.2,"Hours":12, "Minutes":15}
    # res2 = json.dumps(stus)  # 先把字典转成json
    # client.publish('python/mqtt', payload=res2, qos=0)
    # client.publish('emqtt', payload='Hello World', qos=0)
    for i in range(100):
        # 循环发布消息
        publish(client, "mqtt/guangdu", i)
        time.sleep(1)

# 建立连接
# MQTT Broker连接参数
broker = 'broker-cn.emqx.io'
port = 1883
client_id = f'python-mqtt-{random.randint(0, 1000)}'

# 消息发布
run_publish()

三、subcribe订阅消息（mqtt_subcribe.py）

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
import paho.mqtt.client as mqtt
import random

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

# 处理订阅到的消息
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

# MQTT Broker连接参数
broker = 'broker-cn.emqx.io'
port = 1883
client_id = f'python-mqtt-{random.randint(0, 1000)}'

client.connect(broker, port, 600) # 600为keepalive的时间间隔
client.subscribe("mqtt/guangdu", qos=0) # subscribe 订阅

client.loop_forever() # 保持连接

四、测试

1.先把 mqtt_subcribe.py 运行起来（在VS Code）中
2.再把 mqtt_publish.py 在命令行或Windows PowerShell中运行起来python .\mqtt_publish.py

就能看到效果啦。订阅消息的这边一直可以接收到发布出来的消息啦。

所以，在订阅消息的 on_message方法中，可以把消息的主题（msg.topic）和消息的内容（msg.payload）直接存进数据库啦，sqlite和mysql都行。