系统：Ubuntu20.04， windows
软件要求：
（1）下载安装mosquitto
1. Linux通过ppa安装之后会自动启动服务，可以通过systemctl status mosquitto.service查看，默认配置文件路径在/etc/mosquitto/mosquitto.conf，如果修改了conf配置文件，需要重启服务以生效，参考教程https://www.dtmao.cc/news_show_759697.shtml，可以修改配置文件为：

#设置不允许匿名登录
allow_anonymous false
#设置账户密码文件位置为C:\MosquittoTest\pwfile.example
password_file pwfile.example

#把日志信息输入到指定文件
log_dest file mosquittotest.log

#在控制台输出信息，运行win服务无效
log_dest stdout

#不记录
#log_type none
#########下面的debug、error、warning.....等等可以组合使用。
#记录网络通信包，通信包大小（含心跳包），但不显示内容
log_type debug
#错误信息（没见过）
log_type error
#警告信息（没见过）
log_type warning
#设备的订阅信息、发布信息及下线信息（端口、设备名、用户、不包发布内容）
log_type notice
#服务启动关闭信息、版本号、端口号、配置文件信息
log_type information
#所有设备订阅主题提醒
log_type subscribe
#这个没有试出来干啥用的（没见过）

log_type unsubscribe
#websockets链接信息（没见过）

#MQTT协议
port 1883
protocol mqtt

#websockets协议
listener 8000 
protocol websockets

log_type websockets
websockets_log_level 0

2. windows系统下载安装后目录如下图所示：和Linux一样，需要配置 conf文件，另外，pwfile.example是存储用户名的文件，在conf中会用到

（2）安装python mqtt客户端：pip3 install -i https://pypi.doubanio.com/simple paho-mqtt

基本思路

首先在Linux或者windows系统运行mqtt服务程序，等待客户端连接；然后用python编写两个程序，一个用来发布信息，一个用来订阅信息，注意这两个程序都是需要连接到mqtt服务器的，发布信息和订阅信息的程序之间解耦，一切交给mqtt服务器去处理。

1.mqtt发布程序

# -*- coding: utf-8 -*-
"""
Created on Sun Jun 20 09:38:02 2021

@author: Wenqing Zhou (zhou.wenqing@qq.com)
@github: https://github.com/ouening
"""
# 参考链接：
# （1）https://www.cnblogs.com/chenpingzhao/p/11383856.html
# （2）https://www.emqx.cn/blog/how-to-use-mqtt-in-python
# （3）https://www.dtmao.cc/news_show_759697.shtml
import random
import time
import datetime
from paho.mqtt import client as mqtt_client

## ===========方法1===========
# 使用mosquitto服务端程序创建本地的mqtt服务，需要配置mosquitto.conf文件，
# 可以参考https://www.dtmao.cc/news_show_759697.shtml，此时host是127.0.0.1，或者是通过ipconfig（windows）查看本机ip地址
broker = '127.0.0.1'

## ==========方法2============
# 笔者在腾讯云有个带公网ip的ubuntu服务器，通过ppa安装好mosquitto之后，修改conf配置文件，
# 创建用户，重启mosquitto服务
# broker = '服务器ip地址' # 使用公网服务器ip地址

## ==========方法3============
# 使用物联网厂商提供的公共服务器或者私有服务器进行连接，可以参考https://www.emqx.cn/blog/how-to-use-mqtt-in-python
# broker = 'broker.emqx.io'

port = 1883
username = 'kindy'
passwd = 'kindy'
topic = "kindy/topic1"
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 1000)}'

# 连接mqtt服务器
def connect_mqtt():
    def on_exec(strcmd):
        print ("Exec:",strcmd)
    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)
    def on_publish(mqttc, obj, mid):
        print("OnPublish, mid: "+str(mid))
 
    def on_subscribe(mqttc, obj, mid, granted_qos):
        print("Subscribed: "+str(mid)+" "+str(granted_qos))
     
    def on_log(mqttc, obj, level, string):
        print("Log:"+string)
     
    def on_message(mqttc, obj, msg):
        curtime = datetime.datetime.now()
        strcurtime = curtime.strftime("%Y-%m-%d %H:%M:%S")
        print(strcurtime + ": " + msg.topic+" "+str(msg.qos)+" "+str(msg.payload))
        on_exec(str(msg.payload))

    client = mqtt_client.Client(client_id)
    print(client)
    client.on_connect = on_connect
    client.on_log = on_log
    client.on_message = on_message

    # 连接mqtt服务器
    client.username_pw_set(username, password=passwd)
    client.connect(broker, port)

    return client


def publish(client):
    msg_count = 0
    while True:
        time.sleep(1)
        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}")
        msg_count += 1


def run():
    client = connect_mqtt()
    client.loop_start()
    publish(client)


if __name__ == '__main__':
    run()

2. mqtt订阅程序

# -*- coding: utf-8 -*-
"""
Created on Sun Jun 20 09:38:33 2021

@author: Wenqing Zhou (zhou.wenqing@qq.com)
@github: https://github.com/ouening
"""

# 参考链接：
# （1）https://www.cnblogs.com/chenpingzhao/p/11383856.html
# （2）https://www.emqx.cn/blog/how-to-use-mqtt-in-python

# 除了以下通过python程序接收mqtt订阅信息外，还可以下载相关的mqtt客户端程序，例如https://mqttx.app/zh
import random

from paho.mqtt import client as mqtt_client

# broker = 'broker.emqx.io'
# broker = '127.0.0.1'
broker = '服务器ip地址'
port = 1883
username = 'kindy'
passwd = 'kindy'
topic = "kindy/topic1"
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 100)}'


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

    # 连接mqtt服务器
    client.username_pw_set(username, password=passwd)
    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()