Python MQTT客户端未接收消息

我正在使用MQTT Paho项目中的以下代码从我的MQTT代理订阅消息。我使用

mosquitto\u sub

测试了连接，并在那里收到了消息。但是，当我运行下面的代码时，它不会收到任何消息，也不会打印输出。我检查了主题和主持人

import paho.mqtt.client as mqtt

# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, rc):
    print("Connected with result code "+str(rc))
    # Subscribing in on_connect() means that if we lose the connection and
    # reconnect then subscriptions will be renewed.
    client.subscribe("test")

# The callback for when a PUBLISH message is received from the server.
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("localhost", 1883, 60)
client.loop_forever()

代理记录了以下错误：

Invalid protocol "MQTT" in CONNECT from ::1.
Socket read error on client (null), disconnecting.

编辑感谢@hardillb指出过时的MQTT版本

在我做了以下工作之后，一切都正常了：

苏多很容易得到净化

sudo apt添加存储库ppa:mosquitto dev/mosquitto ppa

sudoapt获得更新

sudo-apt-get-install-mosquitto

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这很可能是因为您使用的是旧版本的mosquitto，而python希望有一个支持MQTT 3.1.1的更新版本

尝试更改代码，如图所示：

import paho.mqtt.client as mqtt

# The callback for when the client receives a CONNACK response from the server.
def on_connect(client, userdata, rc):
    print("Connected with result code "+str(rc))
    # Subscribing in on_connect() means that if we lose the connection and
    # reconnect then subscriptions will be renewed.
    client.subscribe("test")

# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
    print(msg.topic+" "+str(msg.payload))

# Change made HERE 
client = mqtt.Client(protocol=MQTTv31)

client.on_connect = on_connect
client.on_message = on_message

client.connect("localhost", 1883, 60)
client.loop_forever()

---

你也应该尽快升级你的代理，这个版本已经过时了，有很多已知的问题，当前的版本是1.4.10

当你说不起作用时，你有任何输出吗？还有，您在哪个平台上运行此操作？完全没有输出。如果您甚至没有收到“已连接结果代码…”消息，那么您应该检查代理日志，看看它是否显示了客户端未连接的原因。您发布的代码在这里运行良好我添加了由brokerWhat broker记录的错误消息，您使用的是什么版本？