WebSocket

Analog also supports WebSockets and Server-Sent Events through Nitro.

Enabling WebSockets

Currently, WebSocket support in Nitro is experimental and it can be enabled in the analog plugin:

vite.config.ts

import { defineConfig } from 'vite';
import analog from '@analogjs/platform';

export default defineConfig({
  // ...
  plugins: [
    analog({
      // ...
      nitro: {
        experimental: {
          websocket: true,
        },
      },
    }),
  ],
  // ...
});

Note: In development, the Vite HMR WebSocket server runs on the same port as the dev server by default. To prevent conflicts, you need to change this port. The dev server port is usually defined in project.json/angular.json, which takes precedence over vite.config.ts. To allow the port settings in vite.config.ts to take effect, remove the port definition from project.json/angular.json. Additionally, you can specify an optional path to easily differentiate connections in the browser dev tools:

vite.config.ts

import { defineConfig } from 'vite';
import analog from '@analogjs/platform';

export default defineConfig({
  // ...
  server: {
    port: 3000, // dev-server port
    hmr: {
      port: 3002, // hmr ws port
      path: 'vite-hmr', // optional
    },
  },
  // ...
});

Defining a WebSocket Handler

Similar to API routes, WebSocket Handlers are defined in the src/server/routes/api folder.

// src/server/api/routes/ws/chat.ts
import { defineWebSocketHandler } from 'h3';

export default defineWebSocketHandler({
  open(peer) {
    peer.send({ user: 'server', message: `Welcome ${peer}!` });
    peer.publish('chat', { user: 'server', message: `${peer} joined!` });
    peer.subscribe('chat');
  },
  message(peer, message) {
    if (message.text().includes('ping')) {
      peer.send({ user: 'server', message: 'pong' });
    } else {
      const msg = {
        user: peer.toString(),
        message: message.toString(),
      };
      peer.send(msg); // echo
      peer.publish('chat', msg);
    }
  },
  close(peer) {
    peer.publish('chat', { user: 'server', message: `${peer} left!` });
  },
});

WebSocket Routes

WebSocket routes are exposed with the same path as API routes. For example, src/server/routes/api/ws/chat is exposed as ws://example.com/api/ws/chat.

Defining a Server-sent Event Handler

Server-sent event handlers can be created using createEventStream function in the event handler.

// src/server/routes/api/sse.ts
import { defineEventHandler, createEventStream } from 'h3';

export default defineEventHandler(async (event) => {
  const eventStream = createEventStream(event);

  const interval = setInterval(async () => {
    await eventStream.push(`Message @ ${new Date().toLocaleTimeString()}`);
  }, 1000);

  eventStream.onClosed(async () => {
    clearInterval(interval);
    await eventStream.close();
  });

  return eventStream.send();
});

More Info

WebSockets are powered by Nitro, h3 and crossws. See the Nitro, h3 and crossws docs for more details.