ws

What is ws?

The 'ws' npm package is a simple to use, fast, and thoroughly tested WebSocket client and server implementation. It provides the necessary tools to build real-time applications with WebSocket support in Node.js.

What are ws's main functionalities?

Creating a WebSocket server

This code sample demonstrates how to create a WebSocket server that listens on port 8080. When a client connects, it sets up an event listener for messages and logs them. It also sends a message 'something' to the client.

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');
});

Creating a WebSocket client

This code sample shows how to create a WebSocket client that connects to a WebSocket server. Once the connection is open, it sends a message 'something' to the server and logs any messages received from the server.

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) {
  console.log(data);
});

Broadcasting to all clients

This code sample illustrates how to broadcast a message to all connected clients except the sender. It loops through all clients and sends the message if the client is not the sender and the connection is open.

const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(data) {
    wss.clients.forEach(function each(client) {
      if (client !== ws && client.readyState === WebSocket.OPEN) {
        client.send(data);
      }
    });
  });
});

Other packages similar to ws

socket.io

Socket.IO is a library that enables real-time, bidirectional and event-based communication between web clients and servers. It's more feature-rich than 'ws', providing built-in support for broadcasting to multiple sockets, handling reconnection, and other high-level features. However, it's also heavier and less minimalistic than 'ws'.

faye-websocket

Faye is a WebSocket (and EventSource) implementation that is designed for ease of use and compatibility across a wide range of browsers. It's similar to 'ws' but also works in client-side JavaScript, unlike 'ws' which is Node.js only.

websocket

The 'websocket' package provides both client and server implementations of the WebSocket protocol. It offers a similar API to 'ws' but also includes a fallback option for older browsers that do not support WebSockets, using Flash sockets or other transport protocols.

README

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

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(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() {
  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

const WebSocketServer = require('ws').Server;
const 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

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

const WebSocketServer = require('ws').Server;
const 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

const WebSocket = require('ws');
const 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