以下使用python的套件
首先安裝paho

pip install paho-mqtt

主程式碼如下

import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print("成功")
        client.subscribe("test/topic")
    else:
        print(f"失败：{rc}")

def on_message(client, userdata, msg):
    print(f"收到訊息：{msg.topic} {msg.payload.decode()}")

client = mqtt.Client()

client.on_connect = on_connect

client.on_message = on_message

# 你的MQTT網址跟port號）
client.connect("mqtt_server_address", 1883, 60)

client.loop_start()

# 指定主题發布
client.publish("test/topic", "Hello, MQTT!")

try:
    while True:
        pass
except KeyboardInterrupt:
    pass

client.disconnect()