为什么在 on_connect 之前调用 on_publish 回调？

Question

我编写的代码的输出是on_publish('Connected', '0')('message received ', 'test1234')('message topic=', u'paho/test')代码如下：import paho.mqtt.client as mqtt  import time import jsondef on_connect(client,data,flag,rc):    print("Connected",str(rc))def on_publish(client,data,msg):    print("on_publish")def on_message(client, userdata, message):    print("message received " ,str(message.payload.decode("utf-8")))    print("message topic=",message.topic)broker_address="iot.eclipse.org"client = mqtt.Client()client.on_connect=on_connectclient.on_publish=on_publish client.on_message=on_message client.connect(broker_address,1883) #connect to broker client.loop_start()  data="test1234" client.subscribe("paho/test") client.publish("paho/test",data) time.sleep(4) # wait client.loop_stop() #stop the loop

Answer 1

移动到电话subscribe和publish到里面on_connect的回调，那么你可以肯定的是，连接已经试图订阅一个主题并发布消息之前成功。

如果经纪人出现问题，其他任何事情都会失败。