> For the complete documentation index, see [llms.txt](https://socket.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://socket.gitbook.io/docs/3-ke-hu-duan-apiclientapi/3.1-io/initialization_examples_with_query_parameters.md).

# 3.1.5 初始化示例-查询参数

```javascript
const socket= io('http://localhost?token=abc');

// 服务端
const io= require('socket.io')()

// 中间件
io.use((socket,next)=>{
    const token = socket.handshake.query.token;
    if (isValid(token)){
        return next();
    }
    return next(new Error("authentication error"))
});

// 然后

io.on('connection',socket=>{
    const token= socket.handshake.query.token
})
```