MQTT入门（2）- 公开的服务Broker

使用MQTT，前提是需要一个服务器Server/Broker，除了自己搭建服务，刚开始时可以使用第三方提供的在线公开的免费Broker服务。使用这些免费Broker服务，可以在刚开始时快速理解MQTT协议。

其他：https://github.com/mqtt/mqtt.github.io/wiki/public_brokers

这些Broker/Server已经搭建好了，只需要编写Client/Subscriber就能测试一下MQTT了。

以使用Python的paho-mqtt来实现客户端。连接test.mosquitto.org服务为例。

（1）安装Eclipse Paho客户端

pip install paho-mqtt

（2）客户端连接

unencrypted-mqtt.py

# coding=utf8
import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("test/rensanning/time")

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

client.connect("test.mosquitto.org", 1883)
client.loop_forever()

执行 python unencrypted-mqtt.py

（2）发布消息

pub-mqtt.py

# coding=utf8
import paho.mqtt.client as mqtt
import time

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

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
client.connect("test.mosquitto.org", 1883)

while client.loop() == 0:
    msg = "test message from Publisher "+time.ctime()
    client.publish("test/rensanning/time", msg, 0, True)
    print("message published")
    time.sleep(1.5)
    pass

执行 python pub-mqtt.py

（3）订阅消息

sub-mqtt.py

# coding=utf8
import paho.mqtt.client as mqtt

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("test/rensanning/time")

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

client.connect("test.mosquitto.org", 1883)
client.loop_forever()

执行 python sub-mqtt.py

同时运行订阅和发布客户端。

加密通信，访问8883端口

先从 http://test.mosquitto.org/ 下载 mosquitto.org.crt文件。

pub-mqtt-tls.py

# coding=utf8
import paho.mqtt.client as mqtt
import time

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

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
client.tls_set("mosquitto.org.crt")
client.connect("test.mosquitto.org", 8883)

while client.loop() == 0:
    msg = "test message from Publisher "+time.ctime()
    client.publish("test/rensanning/time", msg, 0, True)
    print("message published")
    time.sleep(1.5)
    pass

执行 python pub-mqtt-tls.py

MQTT入门（2）- 公开的服务Broker

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