ws: a node.js websocket library

ws is a simple to use WebSocket implementation, up-to-date against RFC-6455, and probably the fastest WebSocket library for node.js.

Passes the quite extensive Autobahn test suite. See http://websockets.github.com/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.

Sending and receiving text data

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

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

ws.on('message', function(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

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

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

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

  ws.send(array, { binary: true, mask: true });
});

Setting mask, as done for the send options above, will cause the data to be masked according to the WebSocket protocol. The same option applies for text data.

Server example

var WebSocketServer = require('ws').Server
  , wss = new WebSocketServer({ port: 8080 });

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

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

ExpressJS example

var server = require('http').createServer()
  , url = require('url')
  , WebSocketServer = require('ws').Server
  , wss = new WebSocketServer({ server: server })
  , express = require('express')
  , app = express()
  , port = 4080;

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

wss.on('connection', function connection(ws) {
  var 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.on('request', app);
server.listen(port, function () { console.log('Listening on ' + server.address().port) });

Server sending broadcast data

var WebSocketServer = require('ws').Server
  , wss = new WebSocketServer({ port: 8080 });

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

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

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-blocks, 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 */ }

echo.websocket.org demo

var WebSocket = require('ws');
var ws = new WebSocket('ws://echo.websocket.org/', {
  protocolVersion: 8,
  origin: 'http://websocket.org'
});

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

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

ws.on('message', function message(data, flags) {
  console.log('Roundtrip time: ' + (Date.now() - parseInt(data)) + 'ms', flags);

  setTimeout(function timeout() {
    ws.send(Date.now().toString(), {mask: true});
  }, 500);
});

Other examples

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

Note that the usage together with Express 3.0 is quite different from Express 2.x. The difference is expressed in the two different serverstats-examples.

Otherwise, see the test cases.

API Docs

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

Changelog

We're using the GitHub releases for changelog entries.

License

MIT