@chanx-js/server

Type-safe WebSocket server for JavaScript and TypeScript. Declare messages once: each action gets a validated, typed handler, groups broadcast across processes, and the whole API is documented as AsyncAPI, from which @chanx-js/codegen generates a typed client.

Runs on Node with ws, Express, Koa, Fastify, Hono, NestJS, Bun and Deno.

Documentation · Getting started · Why chanx-js? · API

npm install @chanx-js/server ws zod

import { createServer } from 'node:http';
import { z } from 'zod';
import {
  PingMessage,
  PongMessage,
  consumer,
  createChanx,
  defineMessage,
} from '@chanx-js/server';
import { asyncapiMiddleware, attachChanx } from '@chanx-js/server/node';

const Chat = defineMessage('chat', z.object({ text: z.string() }));
const Notice = defineMessage('notice', z.object({ text: z.string() }));

const chat = consumer('/ws/chat/{room}', {
  name: 'chat',
  groups: (conn) => [`room.${conn.params.room}`],
})
  .on(PingMessage, { output: PongMessage }, () => PongMessage.create())
  .on(Chat, { output: Notice }, (m, ctx) =>
    ctx.broadcast(Notice.create({ text: m.payload.text })),
  );

const chanx = createChanx({ consumers: [chat] });
const server = createServer(asyncapiMiddleware(chanx)); // docs at /asyncapi
attachChanx(server, chanx);
server.listen(8000);

• Handlers, not if/else: payloads are validated by any Standard Schema library (Zod, Valibot, ArkType) before your handler runs.
• Groups and topics: broadcast to rooms, and let clients subscribe to many streams over one socket. Across processes with @chanx-js/layers.
• Runs anywhere: Node's http, Express, Koa, Fastify, Hono, Bun, Deno, and NestJS. See integrations.
• Testing: an in-process client and broadcast captures, from @chanx-js/server/testing.
• Compatible with Python chanx: same protocol, same AsyncAPI, one Redis shared by both.

MIT licensed.