@startuml
participant client
participant connect
participant logic

client -> connect: 心跳包请求
connect --> client: 心跳包响应

client -> client: 等待一段时间

client -> connect: 心跳包请求
connect --> client: 心跳包响应


connect -> connect: 连续n次没有收到，释放连接
connect -> logic: 通知设备下线
@enduml