---
lang: en
title: 'API docs: socketio.socketioserver.use'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/extensions/socketio
permalink: /doc/en/lb4/apidocs.socketio.socketioserver.use.html
---

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[Home](./index.md) &gt; [@loopback/socketio](./socketio.md) &gt; [SocketIoServer](./socketio.socketioserver.md) &gt; [use](./socketio.socketioserver.use.md)

## SocketIoServer.use() method

Register a sock.io middleware function

<b>Signature:</b>

```typescript
use(fn: SockIOMiddleware): Server<import("socket.io/dist/typed-events").DefaultEventsMap, import("socket.io/dist/typed-events").DefaultEventsMap, import("socket.io/dist/typed-events").DefaultEventsMap, any>;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  fn | [SockIOMiddleware](./socketio.sockiomiddleware.md) |  |

<b>Returns:</b>

Server&lt;import("socket.io/dist/typed-events").DefaultEventsMap, import("socket.io/dist/typed-events").DefaultEventsMap, import("socket.io/dist/typed-events").DefaultEventsMap, any&gt;