Next WS

Add support for WebSockets in Next.js app directory
npm install next-ws ws

🤔 About

next-ws is a simple package that adds WebSocket support to your Next.js app directory. With next-ws, you no longer need to create a separate WebSocket server to handle WebSocket connections. Instead, you can handle WebSocket connections directly in your Next.js API routes.

Important

Next WS is designed for use in server-based environments. It is not suitable for serverless platforms like Vercel, where WebSocket servers are not supported. Furthermore, this plugin is built for the app directory and does not support the older pages directory.

🏓 Table of Contents

• 📦 Installation
• 🚀 Usage
• 🌀 Examples
• 🔒 HTTPS and wss://

📦 Installation

To set up a WebSocket server with next-ws, you need to patch your local Next.js installation. next-ws simplifies this process by providing a CLI command that handles the patching for you. Follow these steps to get started:

1. Install Dependencies: Use your preferred package manager to install next-ws and its peer dependency ws:

   npm install next-ws ws
   pnpm add next-ws ws
   yarn add next-ws ws

2. Add Prepare Script: Add the following prepare script to your package.json. The prepare script is a lifecycle script that runs automatically when you run npm install, ensuring that your Next.js installation is patched with next-ws every time you install it:

   {
     "scripts": {
       "prepare": "next-ws patch"
     }
   }

🚀 Usage

Using WebSocket connections in your Next.js app directory is simple with next-ws. You can handle WebSocket connections directly in your API routes via exported UPGRADE functions.

export function UPGRADE(
  client: import('ws').WebSocket,
  server: import('ws').WebSocketServer,
  request: import('next/server').NextRequest,
  context: import('next-ws/server').RouteContext<'/api/ws'>,
) {
  // ...
}

🌀 Examples

Tip

For more detailed examples, refer the examples directory.

Echo Server

This example demonstrates a simple WebSocket echo server that sends back any message it receives. Create a new API route file anywhere in your app directory and export a UPGRADE function to handle WebSocket connections:

// app/api/ws/route.ts (can be any route file in the app directory)

export function UPGRADE(
  client: import('ws').WebSocket,
  server: import('ws').WebSocketServer
) {
  console.log('A client connected');

  client.on('message', (message) => {
    console.log('Received message:', message);
    client.send(message);
  });

  client.once('close', () => {
    console.log('A client disconnected');
  });
}

You can now connect to your WebSocket server, send it a message and receive the same message back.

Chat Room

See the chat room example.

WebSocket Proxy

Forward connections to another WebSocket server, using a catch-all route to keep the rest of the path. See the websocket proxy example.

🔒 HTTPS and wss://

Next WS doesn't handle TLS itself. It listens for upgrade requests on the same HTTP server that Next.js uses, so wss:// works whenever that server is reachable over HTTPS.

Reverse proxy (recommended): terminate TLS in nginx, Caddy or your load balancer and forward to next start over plain HTTP. Make sure the proxy forwards the Upgrade and Connection headers.

Custom server: create an HTTPS server with your certificate and hand it to Next WS. See the custom server example for the full setup.

import { readFileSync } from 'node:fs';
import { createServer } from 'node:https';
import { setHttpServer } from 'next-ws/server';

const httpsServer = createServer({
  key: readFileSync('key.pem'),
  cert: readFileSync('cert.pem'),
});
setHttpServer(httpsServer);