MQTT subscription problem

[11starry]

在调用 int mqtt_subscribe时；如果订阅后立即有数据下发，可能会出现无法接收到该数据帧的情况，这可能是订阅操作与消息处理机制之间的时序问题。可以在此函数调用MQTTSerialize_subscribe之前，先调用mqtt_msg_handler_create函数，如订阅失败再调用mqtt_msg_handler_destory，通过这种方式，可以确保在订阅动作执行前，消息处理机制已正确配置。个人意见，仅供参考

When calling int mqtt_subscribe; If data is delivered immediately after subscribing, there may be a situation where the data frame cannot be received, which may be a timing issue between the subscription operation and the message processing mechanism. You can call the mqtt_msg_handler_create function before this function calls MQTTSerialize_subscribe, and then call mqtt_msg_handler_destory if the subscription fails. This way, you can ensure that before the subscription action is executed, The message handling mechanism is configured correctly. Personal opinion, for reference only

[qulei123]

我好像理解你的意思了：订阅消息已经发送出去了，但是此时还没有执行到 mqtt_ack_list_record(SUBACK)，SUBACK响应已经过来了，导致订阅失败。所以需要先mqtt_ack_list_record(SUBACK)，再发送订阅消息 ？？？