bug report

```
KEEPALIVE：检测到后端服务器 59.172.37.6:64943 掉线
释放端口 38001
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Os { code: 107, kind: NotConnected, message: "Transport endpoint is not connected" }', src/main.rs:74:47
```