# ServerAndEventStreamsFactory

**Kind:** Class

**Source:** [`packages/websockets/factories/server-and-event-streams-factory.ts`](https://github.com/nestjs/nest/blob/master/packages/websockets/factories/server-and-event-streams-factory.ts#L4)

**Part of:** [Websockets](subsystem-packages-websockets)

`ServerAndEventStreamsFactory` creates a `ServerAndEventStreamsHost<T>` around an existing WebSocket server instance. It provides the WebSocket layer with a consistent host object that can expose the underlying server and its event-stream capabilities to the rest of the framework.

## Methods

| Method | Signature | Returns |
|---|---|---|
| `create` | `create(server: T)` | `ServerAndEventStreamsHost<T>` |

## Diagram

```mermaid
graph LR
  A[WebSocket Adapter / Server] --> B[ServerAndEventStreamsFactory]
  B -->|create()| C[ServerAndEventStreamsHost<T>]
  C --> D[WebSocket Server Instance]
  C --> E[Event Stream Handlers]
```

## Usage

```ts
import { Server } from 'socket.io';
import { ServerAndEventStreamsFactory } from '@nestjs/websockets/factories/server-and-event-streams-factory';

const io = new Server(3000, {
  cors: {
    origin: '*',
  },
});

const factory = new ServerAndEventStreamsFactory();
const host = factory.create<Server>(io);

// Access the wrapped server through the host.
host.server.on('connection', socket => {
  socket.emit('connected', { message: 'Welcome!' });
});
```

## AI Coding Instructions

- Use this factory when framework code needs a `ServerAndEventStreamsHost<T>` rather than a raw WebSocket server instance.
- Preserve the generic server type (`T`) so adapter-specific APIs, such as Socket.IO methods, remain type-safe.
- Pass an already initialized server instance; this factory wraps server/event-stream infrastructure and should not be responsible for server startup configuration.
- Keep adapter-specific behavior outside the factory—implement transport setup and connection options in the WebSocket adapter or bootstrap layer.
- Treat this as framework infrastructure; prefer public WebSocket module APIs in application code when available.

## How it works

## `ServerAndEventStreamsFactory`

`ServerAndEventStreamsFactory` is an exported class with one static method, `create<T = any>(server)`, which constructs a `ServerAndEventStreamsHost<T>` around a supplied server value. [server-and-event-streams-factory.ts:4-5](packages/websockets/factories/server-and-event-streams-factory.ts#L4-L5)