ws 8.21.3: WebSocketServer

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify ws.WebSocketServer in pkg:npm/ws@8.21.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/ws@8.21.3
Demonstrate these symbols/APIs:
  - ws.WebSocketServer

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:42637672fd8bc0e232a8257eac9423bc17372a231178775f2495719fa748d7b7","contract":["assert WebSocketServer initializes with port and host","assert WebSocketServer emits connection event with socket and incoming request","assert WebSocketServer tracks active clients in clients Set and removes on disconnect","assert WebSocketServer broadcasts messages to multiple connected clients","assert WebSocketServer closes cleanly and emits close event"],"goal":"verify ws.WebSocketServer in pkg:npm/ws@8.21.3","kind":"HOW","packages":["pkg:npm/ws@8.21.3"],"schemaVersion":1,"symbols":["ws.WebSocketServer"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/ws@8.21.3"],"schemaVersion":1,"subject":"pkg:npm/ws@8.21.3","symbols":["ws.WebSocketServer"],"verifierAdapter":"node-typescript@1"}

import WebSocket, { WebSocketServer } from 'ws';

/**
 * Creates and starts a WebSocketServer instance.
 * @param {import('ws').ServerOptions} [options]
 * @param {Function} [callback]
 * @returns {WebSocketServer}
 */
export function createWebSocketServer(options = {}, callback) {
  return new WebSocketServer(options, callback);
}

/**
 * Broadcasts a message to all connected clients on a WebSocketServer.
 * @param {WebSocketServer} server
 * @param {any} data
 * @param {object} [options]
 */
export function broadcast(server, data, options) {
  for (const client of server.clients) {
    if (client.readyState === WebSocket.OPEN) {
      client.send(data, options);
    }
  }
}

export { WebSocket, WebSocketServer };

{
  "name": "sample-ws-websocketserver",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-ws-websocketserver",
      "version": "1.0.0",
      "dependencies": {
        "ws": "8.21.3"
      }
    },
    "node_modules/ws": {
      "version": "8.21.3",
      "resolved": "https://registry.npmjs.org/ws/-/ws-8.21.3.tgz",
      "integrity": "sha512-201TZ/kPWxoPr/OKWjquZR1SWKXcvxdH+e1xrx89b3YbmzLMFCLfnaG1HFIgWzJOEWZ7MvpK++odZufgYR50Rw==",
      "license": "MIT",
      "engines": {
        "node": ">=10.0.0"
      },
      "peerDependencies": {
        "bufferutil": "^4.0.1",
        "utf-8-validate": ">=5.0.2"
      },
      "peerDependenciesMeta": {
        "bufferutil": {
          "optional": true
        },
        "utf-8-validate": {
          "optional": true
        }
      }
    }
  }
}

{
  "name": "sample-ws-websocketserver",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "dependencies": {
    "ws": "8.21.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify ws.WebSocketServer in pkg:npm/ws@8.21.3",
  "kind": "HOW",
  "packages": [
    "pkg:npm/ws@8.21.3"
  ],
  "symbols": [
    "ws.WebSocketServer"
  ]
}

import assert from 'node:assert/strict';
import { createWebSocketServer, broadcast, WebSocket, WebSocketServer } from '../index.mjs';

// 1. assert WebSocketServer initializes with port and host
{
  const wss = createWebSocketServer({ host: '127.0.0.1', port: 0 });
  await new Promise((resolve) => wss.on('listening', resolve));
  const address = wss.address();
  assert.strictEqual(typeof address, 'object');
  assert.strictEqual(address.address, '127.0.0.1');
  assert.ok(address.port > 0);
  await new Promise((resolve) => wss.close(resolve));
}

// 2. assert WebSocketServer emits connection event with socket and incoming request
{
  const wss = createWebSocketServer({ host: '127.0.0.1', port: 0 });
  await new Promise((resolve) => wss.on('listening', resolve));
  const port = wss.address().port;

  let serverReqUrl = null;
  let serverWs = null;
  wss.on('connection', (ws, req) => {
    serverWs = ws;
    serverReqUrl = req.url;
  });

  const client = new WebSocket(`ws://127.0.0.1:${port}/test-path?param=val`);
  await new Promise((resolve, reject) => {
    client.on('open', resolve);
    client.on('error', reject);
  });

  assert.ok(serverWs !== null);
  assert.strictEqual(serverWs.readyState, WebSocket.OPEN);
  assert.strictEqual(serverReqUrl, '/test-path?param=val');

  client.close();
  await new Promise((r) => client.on('close', r));
  await new Promise((r) => wss.close(r));
}

// 3. assert WebSocketServer tracks active clients in clients Set and removes on disconnect
{
  const wss = createWebSocketServer({ host: '127.0.0.1', port: 0 });
  await new Promise((resolve) => wss.on('listening', resolve));
  const port = wss.address().port;

  assert.strictEqual(wss.clients.size, 0);

  const client1 = new WebSocket(`ws://127.0.0.1:${port}`);
  await new Promise((r) => client1.on('open', r));
  assert.strictEqual(wss.clients.size, 1);

  const client2 = new WebSocket(`ws://127.0.0.1:${port}`);
  await new Promise((r) => client2.on('open', r));
  assert.strictEqual(wss.clients.size, 2);

  client1.close();
  await new Promise((r) => client1.on('close', r));
  await new Promise((r) => setTimeout(r, 50));
  assert.strictEqual(wss.clients.size, 1);

  client2.close();
  await new Promise((r) => client2.on('close', r));
  await new Promise((r) => setTimeout(r, 50));
  assert.strictEqual(wss.clients.size, 0);

  await new Promise((r) => wss.close(r));
}

// 4. assert WebSocketServer broadcasts messages to multiple connected clients
{
  const wss = createWebSocketServer({ host: '127.0.0.1', port: 0 });
  await new Promise((resolve) => wss.on('listening', resolve));
  const port = wss.address().port;

  const client1 = new WebSocket(`ws://127.0.0.1:${port}`);
  const client2 = new WebSocket(`ws://127.0.0.1:${port}`);

  await Promise.all([
    new Promise((r) => client1.on('open', r)),
    new Promise((r) => client2.on('open', r))
  ]);

  const msgPromise1 = new Promise((resolve) => client1.on('message', (d) => resolve(d.toString('utf8'))));
  const msgPromise2 = new Promise((resolve) => client2.on('message', (d) => resolve(d.toString('utf8'))));

  broadcast(wss, 'broadcast payload');

  const [res1, res2] = await Promise.all([msgPromise1, msgPromise2]);
  assert.strictEqual(res1, 'broadcast payload');
  assert.strictEqual(res2, 'broadcast payload');

  client1.close();
  client2.close();
  await Promise.all([
    new Promise((r) => client1.on('close', r)),
    new Promise((r) => client2.on('close', r))
  ]);
  await new Promise((r) => wss.close(r));
}

// 5. assert WebSocketServer closes cleanly and emits close event
{
  const wss = createWebSocketServer({ host: '127.0.0.1', port: 0 });
  await new Promise((resolve) => wss.on('listening', resolve));

  let closeEventFired = false;
  wss.on('close', () => {
    closeEventFired = true;
  });

  await new Promise((resolve) => wss.close(resolve));
  assert.strictEqual(closeEventFired, true);
}

console.log('Contract tests passed successfully.');