@nestjs/websockets

WebSocket Gateway

This feature allows you to create a WebSocket gateway that listens for incoming WebSocket connections and messages. The `@WebSocketGateway` decorator is used to define a WebSocket gateway, and the `@SubscribeMessage` decorator is used to handle specific message events.

```typescript
import { WebSocketGateway, WebSocketServer, SubscribeMessage, MessageBody } from '@nestjs/websockets';
import { Server } from 'socket.io';

@WebSocketGateway()
export class ChatGateway {
  @WebSocketServer()
  server: Server;

  @SubscribeMessage('message')
  handleMessage(@MessageBody() message: string): void {
    this.server.emit('message', message);
  }
}
```

WebSocket Client

This feature allows you to create a WebSocket client that can connect to a WebSocket server. The `@WebSocketClient` decorator is used to define a WebSocket client, and the `OnGatewayInit`, `OnGatewayConnection`, and `OnGatewayDisconnect` interfaces are used to handle client lifecycle events.

```typescript
import { Injectable } from '@nestjs/common';
import { WebSocketClient, OnGatewayInit, OnGatewayConnection, OnGatewayDisconnect } from '@nestjs/websockets';
import { Socket } from 'socket.io-client';

@Injectable()
@WebSocketClient()
export class ChatClient implements OnGatewayInit, OnGatewayConnection, OnGatewayDisconnect {
  private client: Socket;

  afterInit(client: Socket) {
    this.client = client;
    console.log('WebSocket client initialized');
  }

  handleConnection(client: Socket) {
    console.log('Client connected:', client.id);
  }

  handleDisconnect(client: Socket) {
    console.log('Client disconnected:', client.id);
  }
}
```

Custom WebSocket Server

This feature allows you to create a custom WebSocket server using the `ws` library. The `@WebSocketGateway` decorator can accept a custom server instance, and you can handle connection and message events directly.

```typescript
import { WebSocketGateway, WebSocketServer } from '@nestjs/websockets';
import { Server } from 'ws';

@WebSocketGateway({ server: new Server({ port: 8080 }) })
export class CustomGateway {
  @WebSocketServer()
  server: Server;

  constructor() {
    this.server.on('connection', (socket) => {
      socket.on('message', (message) => {
        console.log('Received message:', message);
      });
    });
  }
}
```