engine.io-client 6.6.6: verify engine.io-client WebSocket transport and binary packet transmission

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 engine.io-client WebSocket transport and binary packet transmission
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/engine.io-client@6.6.6
Demonstrate these symbols/APIs:
  - WebSocket
  - transports.websocket

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:sha256:747c788036ac57c2fdef0989efbe2ac7a5596fd5b6b8f41d8033db62e26925d3","contract":["WebSocket transport class is exported and inherits from Transport","Socket initializes with direct WebSocket transport configuration without upgrade","Socket connects to WebSocket server and completes handshake establishing open state","Socket sends and receives text message packets over WebSocket transport","Socket sends and receives binary Buffer and ArrayBuffer payloads over WebSocket transport","Socket closes cleanly over WebSocket transport transitioning readyState to closed","Socket emits error and close events when connecting to unreachable WebSocket endpoint"],"goal":"verify engine.io-client WebSocket transport and binary packet transmission","kind":"HOW","packages":["pkg:npm/engine.io-client@6.6.6"],"schemaVersion":1,"symbols":["WebSocket","transports.websocket"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/engine.io-client@6.6.6"],"schemaVersion":1,"subject":"pkg:npm/engine.io-client@6.6.6","symbols":["WebSocket","transports.websocket"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-engine-io-client-websocket",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-engine-io-client-websocket",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "engine.io-client": "6.6.6"
      }
    },
    "node_modules/@socket.io/component-emitter": {
      "version": "3.1.2",
      "resolved": "https://registry.npmjs.org/@socket.io/component-emitter/-/component-emitter-3.1.2.tgz",
      "integrity": "sha512-9BCxFwvbGg/RsZK9tjXd8s4UcwR0MWeFQ1XEKIQVVvAGJyINdrqKMcTRyLoK8Rse1GjzLV9cwjWV1olXRWEXVA==",
      "license": "MIT"
    },
    "node_modules/debug": {
      "version": "4.4.3",
      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz",
      "integrity": "sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==",
      "license": "MIT",
      "dependencies": {
        "ms": "^2.1.3"
      },
      "engines": {
        "node": ">=6.0"
      },
      "peerDependenciesMeta": {
        "supports-color": {
          "optional": true
        }
      }
    },
    "node_modules/engine.io-client": {
      "version": "6.6.6",
      "resolved": "https://registry.npmjs.org/engine.io-client/-/engine.io-client-6.6.6.tgz",
      "integrity": "sha512-iY6QdftLQ9pyiPoX082bpf/u1UewnOaJrtJIF9T0++QB34lZrj0uP+Q/bj8AlUsAxqhnkTV2BS8SBZSxOmoV5Q==",
      "license": "MIT",
      "dependencies": {
        "@socket.io/component-emitter": "~3.1.0",
        "debug": "~4.4.1",
        "engine.io-parser": "~5.2.1",
        "ws": "~8.21.0",
        "xmlhttprequest-ssl": "~2.1.1"
      }
    },
    "node_modules/engine.io-parser": {
      "version": "5.2.3",
      "resolved": "https://registry.npmjs.org/engine.io-parser/-/engine.io-parser-5.2.3.tgz",
      "integrity": "sha512-HqD3yTBfnBxIrbnM1DoD6Pcq8NECnh8d4As1Qgh0z5Gg3jRRIqijury0CL3ghu/edArpUYiYqQiDUQBIs4np3Q==",
      "license": "MIT",
      "engines": {
        "node": ">=10.0.0"
      }
    },
    "node_modules/ms": {
      "version": "2.1.3",
      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
      "integrity": "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==",
      "license": "MIT"
    },
    "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
        }
      }
    },
    "node_modules/xmlhttprequest-ssl": {
      "version": "2.1.2",
      "resolved": "https://registry.npmjs.org/xmlhttprequest-ssl/-/xmlhttprequest-ssl-2.1.2.tgz",
      "integrity": "sha512-TEU+nJVUUnA4CYJFLvK5X9AOeH4KvDvhIfm0vV1GaQRtchnG0hgK5p8hw/xjv8cunWYCsiPCSDzObPyhEwq3KQ==",
      "engines": {
        "node": ">=0.4.0"
      }
    }
  }
}

{
  "name": "sample-engine-io-client-websocket",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification sample for engine.io-client WebSocket transport and binary packet transmission",
  "main": "src/index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "engine.io-client": "6.6.6"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify engine.io-client WebSocket transport and binary packet transmission",
  "kind": "HOW",
  "packages": [
    "pkg:npm/engine.io-client@6.6.6"
  ],
  "symbols": [
    "WebSocket",
    "transports.websocket"
  ]
}

'use strict';

const {
  Socket,
  Transport,
  transports,
  WebSocket,
  NodeWebSocket
} = require('engine.io-client');

/**
 * Creates an Engine.IO client socket configured for direct WebSocket transport.
 * @param {string|object} uri - Target server URI
 * @param {object} [opts] - Connection options
 * @returns {Socket}
 */
function createWebSocketClient(uri, opts = {}) {
  return new Socket(uri, {
    transports: ['websocket'],
    upgrade: false,
    ...opts
  });
}

module.exports = {
  Socket,
  Transport,
  transports,
  WebSocket,
  NodeWebSocket,
  createWebSocketClient
};

'use strict';

const assert = require('assert');
const http = require('http');
const { WebSocketServer } = require('ws');
const {
  Socket,
  Transport,
  transports,
  WebSocket,
  NodeWebSocket,
  createWebSocketClient
} = require('../src/index.js');

async function main() {
  // 1. WebSocket transport class is exported and inherits from Transport
  {
    assert.strictEqual(typeof transports.websocket, 'function');
    assert.strictEqual(typeof WebSocket, 'function');
    assert.strictEqual(typeof NodeWebSocket, 'function');
    assert.strictEqual(typeof createWebSocketClient, 'function');
    assert.strictEqual(transports.websocket.prototype instanceof Transport, true);
    assert.strictEqual(WebSocket.prototype instanceof Transport, true);
  }

  // 2. Socket initializes with direct WebSocket transport configuration without upgrade
  {
    const socket = createWebSocketClient('ws://127.0.0.1:3000');
    assert.strictEqual(socket.readyState, 'opening');
    assert.strictEqual(socket.binaryType, 'nodebuffer');
    assert.deepStrictEqual(socket.transports, ['websocket']);
    socket.close();
    assert.strictEqual(socket.readyState, 'closed');
  }

  // 3. Socket connects to WebSocket server and completes handshake establishing open state
  // 4. Socket sends and receives text message packets over WebSocket transport
  // 5. Socket sends and receives binary Buffer and ArrayBuffer payloads over WebSocket transport
  // 6. Socket closes cleanly over WebSocket transport transitioning readyState to closed
  {
    const server = http.createServer();
    const wss = new WebSocketServer({ server });
    const sessionId = 'eio-ws-proof-sid';

    wss.on('connection', (ws, req) => {
      assert.strictEqual(req.url.includes('transport=websocket'), true);
      assert.strictEqual(req.url.includes('EIO=4'), true);

      const handshake = JSON.stringify({
        sid: sessionId,
        upgrades: [],
        pingInterval: 25000,
        pingTimeout: 20000,
        maxPayload: 1000000
      });
      ws.send('0' + handshake);

      ws.on('message', (data, isBinary) => {
        if (isBinary) {
          ws.send(data, { binary: true });
        } else {
          const str = data.toString();
          if (str === '2') {
            ws.send('3');
          } else if (str.startsWith('4')) {
            const content = str.slice(1);
            ws.send('4echo:' + content);
          }
        }
      });
    });

    await new Promise((resolve) => server.listen(0, '127.0.0.1', resolve));
    const port = server.address().port;

    const socket = createWebSocketClient(`ws://127.0.0.1:${port}`);

    let handshakePayload = null;
    socket.on('handshake', (data) => {
      handshakePayload = data;
    });

    await new Promise((resolve, reject) => {
      socket.on('open', resolve);
      socket.on('error', reject);
    });

    // 3. Handshake and open state verification
    assert.strictEqual(socket.readyState, 'open');
    assert.strictEqual(socket.id, sessionId);
    assert.strictEqual(socket.transport.name, 'websocket');
    assert.strictEqual(handshakePayload.sid, sessionId);
    assert.strictEqual(handshakePayload.pingInterval, 25000);

    // 4. Text packet exchange
    const textPromise = new Promise((resolve) => {
      const onMsg = (msg) => {
        if (typeof msg === 'string') {
          socket.off('message', onMsg);
          resolve(msg);
        }
      };
      socket.on('message', onMsg);
    });
    socket.send('hello-eio-ws');
    const echoedText = await textPromise;
    assert.strictEqual(echoedText, 'echo:hello-eio-ws');

    // 5. Binary packet exchange (Buffer)
    const bufferPromise = new Promise((resolve) => {
      const onMsg = (msg) => {
        if (Buffer.isBuffer(msg)) {
          socket.off('message', onMsg);
          resolve(msg);
        }
      };
      socket.on('message', onMsg);
    });
    const expectedBuf = Buffer.from([10, 20, 30, 40, 50]);
    socket.send(expectedBuf);
    const echoedBuf = await bufferPromise;
    assert.strictEqual(Buffer.compare(echoedBuf, expectedBuf), 0);

    // 5. Binary packet exchange (ArrayBuffer)
    socket.binaryType = 'arraybuffer';
    assert.strictEqual(socket.binaryType, 'arraybuffer');

    const abPromise = new Promise((resolve) => {
      const onMsg = (msg) => {
        if (msg instanceof ArrayBuffer) {
          socket.off('message', onMsg);
          resolve(msg);
        }
      };
      socket.on('message', onMsg);
    });
    const rawUint8 = new Uint8Array([99, 88, 77, 66]);
    socket.send(rawUint8.buffer);
    const echoedAb = await abPromise;
    assert.deepStrictEqual(Array.from(new Uint8Array(echoedAb)), [99, 88, 77, 66]);

    // 6. Clean close
    let closed = false;
    await new Promise((resolve) => {
      socket.on('close', (reason) => {
        closed = true;
        assert.strictEqual(reason, 'forced close');
        resolve();
      });
      socket.close();
    });
    assert.strictEqual(closed, true);
    assert.strictEqual(socket.readyState, 'closed');

    await new Promise((resolve) => server.close(resolve));
  }

  // 7. Socket emits error and close events when connecting to unreachable WebSocket endpoint
  {
    const deadSocket = createWebSocketClient('ws://127.0.0.1:59998');
    let errorFired = false;
    await new Promise((resolve) => {
      deadSocket.on('error', () => {
        errorFired = true;
      });
      deadSocket.on('close', () => {
        resolve();
      });
    });
    assert.strictEqual(errorFired, true);
    assert.strictEqual(deadSocket.readyState, 'closed');
  }

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

main().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
});