在 Python 中使用 MQTT的方法

Dawn ·

更新时间:2024-09-21

· 793 次阅读

Python 是一种广泛使用的解释型、高级编程、通用型编程语言。Python 的设计哲学强调代码的可读性和简洁的语法（尤其是使用空格缩进划分代码块，而非使用大括号或者关键词）。Python 让开发者能够用更少的代码表达想法，不管是小型还是大型程序，该语言都试图让程序的结构清晰明了。

MQTT 是一种基于发布/订阅模式的轻量级物联网消息传输协议，可以用极少的代码和带宽为联网设备提供实时可靠的消息服务，它广泛应用于物联网、移动互联网、智能硬件、车联网、电力能源等行业。

本文主要介绍如何在 Python 项目中使用 paho-mqtt 客户端库，实现客户端与 MQTT 服务器的连接、订阅、取消订阅、收发消息等功能。

项目初始化

本项目使用 Python 3.6 进行开发测试，读者可用如下命令确认 Python 的版本。


➜ ~ python3 --version  
Python 3.6.7

选择 MQTT 客户端库

paho-mqtt 是目前 Python 中使用较多的 MQTT 客户端库，它在 Python 2.7 或 3.x 上为客户端类提供了对 MQTT v3.1 和 v3.1.1 的支持。它还提供了一些帮助程序功能，使将消息发布到 MQTT 服务器变得非常简单。

Pip 安装 Paho MQTT 客户端

Pip 是 Python 包管理工具，该工具提供了对 Python 包的查找、下载、安装、卸载的功能。


pip3 install -i https://pypi.doubanio.com/simple paho-mqtt

Python MQTT 使用 连接 MQTT 服务器

本文将使用 EMQ X 提供的免费公共 MQTT 服务器，该服务基于 EMQ X 的 MQTT 物联网云平台创建。服务器接入信息如下：

Broker: broker.emqx.io TCP Port: 1883 Websocket Port: 8083
导入 Paho MQTT客户端


from paho.mqtt import client as mqtt_client

设置 MQTT Broker 连接参数

设置 MQTT Broker 连接地址，端口以及 topic，同时我们调用 Python random.randint 函数随机生成 MQTT 客户端 id。


broker = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt"
client_id = f'python-mqtt-{random.randint(0, 1000)}'

编写 MQTT 连接函数

编写连接回调函数 on_connect ，该函数将在客户端连接后被调用，在该函数中可以依据 rc 来判断客户端是否连接成功。通常同时我们将创建一个 MQTT 客户端，该客户端将连接到 broker.emqx.io 。


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

首先定义一个 while 循环语句，在循环中我们将设置每秒调用 MQTT 客户端 publish 函数向 /python/mqtt 主题发送消息。


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

订阅消息

编写消息回调函数 on_message ，该函数将在客户端从 MQTT Broker 收到消息后被调用，在该函数中我们将打印出订阅的 topic 名称以及接收到的消息内容。


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

完整代码 消息发布代码


# python 3.6
import random
import time
from paho.mqtt import client as mqtt_client
broker = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt"
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 1000)}'
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)
 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"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()

消息订阅代码


# python 3.6
import random
import time
from paho.mqtt import client as mqtt_client
broker = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt"
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 1000)}'
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)
 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"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()
消息订阅代码
# python3.6
import random
from paho.mqtt import client as mqtt_client
broker = 'broker.emqx.io'
port = 1883
topic = "/python/mqtt"
# 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
 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()

测试 消息发布

运行 MQTT 消息发布代码，我们将看到客户端连接成功，并且成功将消息发布。

python3 pub.py