python - MQTT客户端收不到消息

Question

我正在使用 MQTT Paho 项目中的以下代码来订阅来 self 的 mqtt 代理的消息。我使用 mosquitto_sub 测试了连接，并在那里收到了消息。但是，当我运行以下代码时，它没有收到任何消息，也没有打印任何输出。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。

在我执行以下操作后一切正常:

1. sudo apt-get purge mosquitto
2. sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
3. sudo apt-get update
4. sudo apt-get install mosquitto

Answer 1

这很可能是因为您使用的是旧版本的 mosquitto，而 python 需要支持 MQTT 3.1.1 的新版本

尝试更改代码，如下所示:

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()

您还应该尽快升级您的经纪商，该版本已经过时，并且存在许多已知问题，当前版本是 1.4.10