CONNACK
DISCONNECT (MQTT 5.0)
Subscriber
Broker
PUBLISH / 其他交互
Client
检测到连接丢失触发will遗嘱消息
存储遗嘱消息
异常退出
CONNECTWill Topic = \"device/status\"Will Payload = \"offline\"Will QoS = 1Will Retain = trueWill Delay Interval = 30
运行
正常退出
遗嘱消息仍在存储中等待异常断开
(网络中断 / 崩溃 / 超时)
PUBLISH (topic=\"device/status\
连接
