ws: a Node.js WebSocket library

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ws is a simple to use, blazing fast, and thoroughly tested WebSocket client and server implementation.

Passes the quite extensive Autobahn test suite. See http://websockets.github.io/ws/ for the full reports.

Protocol support

  • HyBi drafts 07-12 (Use the option protocolVersion: 8)
  • HyBi drafts 13-17 (Current default, alternatively option protocolVersion: 13)

Installing

npm install --save ws

Opt-in for performance

There are 2 optional modules that can be installed along side with the ws module. These modules are binary addons which improve certain operations, but as they are binary addons they require compilation which can fail if no c++ compiler is installed on the host system.

  • npm install --save bufferutil: Improves internal buffer operations which allows for faster processing of masked WebSocket frames and general buffer operations.
  • npm install --save utf-8-validate: The specification requires validation of invalid UTF-8 chars, some of these validations could not be done in JavaScript hence the need for a binary addon. In most cases you will already be validating the input that you receive for security purposes leading to double validation. But if you want to be 100% spec-conforming and have fast validation of UTF-8 then this module is a must.

API Docs

See /doc/ws.md for Node.js-like docs for the ws classes.

WebSocket compression

ws supports the permessage-deflate extension extension which enables the client and server to negotiate a compression algorithm and its parameters, and then selectively apply it to the data payloads of each WebSocket message.

The extension is enabled by default but adds a significant overhead in terms of performance and memory comsumption. We suggest to use WebSocket compression only if it is really needed.

To disable the extension you can set the perMessageDeflate option to false. On the server:

const WebSocket = require('ws');

const wss = new WebSocket.Server({
  perMessageDeflate: false,
  port: 8080
});

On the client:

const WebSocket = require('ws');

const ws = new WebSocket('ws://www.host.com/path', {
  perMessageDeflate: false
});

Usage examples

Sending and receiving text data

const WebSocket = require('ws');

const ws = new WebSocket('ws://www.host.com/path');

ws.on('open', function open() {
  ws.send('something');
});

ws.on('message', function incoming(data, flags) {
  // flags.binary will be set if a binary data is received.
  // flags.masked will be set if the data was masked.
});

Sending binary data

const WebSocket = require('ws');

const ws = new WebSocket('ws://www.host.com/path');

ws.on('open', function open() {
  const array = new Float32Array(5);

  for (var i = 0; i < array.length; ++i) {
    array[i] = i / 2;
  }

  ws.send(array);
});

Server example

const WebSocket = require('ws');

const wss = new WebSocket.Server({ port: 8080 });

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  ws.send('something');
});

Broadcast example

const WebSocket = require('ws');

const wss = new WebSocket.Server({ port: 8080 });

// Broadcast to all.
wss.broadcast = function broadcast(data) {
  wss.clients.forEach(function each(client) {
    if (client.readyState === WebSocket.OPEN) {
      client.send(data);
    }
  });
};

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(data) {
    // Broadcast to everyone else.
    wss.clients.forEach(function each(client) {
      if (client !== ws && client.readyState === WebSocket.OPEN) {
        client.send(data);
      }
    });
  });
});

ExpressJS example

const express = require('express');
const http = require('http');
const url = require('url');
const WebSocket = require('ws');

const app = express();

app.use(function (req, res) {
  res.send({ msg: "hello" });
});

const server = http.createServer(app);
const wss = new WebSocket.Server({ server });

wss.on('connection', function connection(ws) {
  const location = url.parse(ws.upgradeReq.url, true);
  // You might use location.query.access_token to authenticate or share sessions
  // or ws.upgradeReq.headers.cookie (see http://stackoverflow.com/a/16395220/151312)

  ws.on('message', function incoming(message) {
    console.log('received: %s', message);
  });

  ws.send('something');
});

server.listen(8080, function listening() {
  console.log('Listening on %d', server.address().port);
});

echo.websocket.org demo

const WebSocket = require('ws');

const ws = new WebSocket('wss://echo.websocket.org/', {
  origin: 'https://websocket.org'
});

ws.on('open', function open() {
  console.log('connected');
  ws.send(Date.now());
});

ws.on('close', function close() {
  console.log('disconnected');
});

ws.on('message', function incoming(data, flags) {
  console.log(`Roundtrip time: ${Date.now() - data} ms`, flags);

  setTimeout(function timeout() {
    ws.send(Date.now());
  }, 500);
});

Other examples

For a full example with a browser client communicating with a ws server, see the examples folder.

Otherwise, see the test cases.

Error handling best practices

// If the WebSocket is closed before the following send is attempted
ws.send('something');

// Errors (both immediate and async write errors) can be detected in an optional
// callback. The callback is also the only way of being notified that data has
// actually been sent.
ws.send('something', function ack(error) {
  // If error is not defined, the send has been completed, otherwise the error
  // object will indicate what failed.
});

// Immediate errors can also be handled with `try...catch`, but **note** that
// since sends are inherently asynchronous, socket write failures will *not* be
// captured when this technique is used.
try { ws.send('something'); }
catch (e) { /* handle error */ }

Changelog

We're using the GitHub releases for changelog entries.

License

MIT