# 4.3.25 event\_disconnect

* `reason` (String) 断开连接的原因（客户端或服务器端）

断开时触发

```javascript
io.on('connection',socket=>{
    socket.on('disconnect',reason=>{
        // ...
    })
})
```

可能的原因：

| 原因                            | 所在端 | 描述                                      |
| ----------------------------- | --- | --------------------------------------- |
| `transport error` 传输错误        | 服务端 | 传输错误                                    |
| `server namespace disconnect` | 服务端 | 服务端执行 `socket.disconnect()`             |
| `client namespace disconnect` | 客户端 | 从客户端获取断开数据包                             |
| `ping timeout`                | 客户端 | 客户端在允许的时间内停止响应Ping（根据`pingTimeout`配置设置） |
| `transport close`             | 客户端 | 客户端停止发送数据                               |
|                               |     |                                         |


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