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1

发生异常: ValueError

Unsupported callback API version: version 2.0 added a callback_api_version, see migrations.md for details

ValueError: Unsupported callback API version: version 2.0 added a callback_api_version, see migrations.md for details

python：3.8.10
paho-mqtt：2.0.0

2

hi, paho-mqtt 2.0 做了较大的修改，您可以参考英文博客修改代码: How to Use MQTT in Python with Paho Client | EMQ

paho-mqtt 迁移指南: https://eclipse.dev/paho/files/paho.mqtt.python/html/migrations.html

3

以下是 paho-mqtt 2.0 的代码

pub.py

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, reason_code, properties):
        if reason_code == 0:
            print("Connected to MQTT Broker!")
        else:
            print("Failed to connect, return code %d\n", reason_code)

    client = mqtt_client.Client(client_id=client_id, callback_api_version=mqtt_client.CallbackAPIVersion.VERSION2)
    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()

sub.py

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, reason_code, properties):
        if reason_code == 0:
            print("Connected to MQTT Broker!")
        else:
            print("Failed to connect, return code %d\n", reason_code)

    client = mqtt_client.Client(client_id=client_id, callback_api_version=mqtt_client.CallbackAPIVersion.VERSION2)
    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()