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://einaros.github.com/ws for the full reports.

Comes with a command line utility, wscat, which can either act as a server (--listen), or client (--connect); Use it to debug simple websocket services.

Protocol support

• Hixie draft 76 (Old and deprecated, but still in use by Safari and Opera. Added to ws version 0.4.2, but server only. Can be disabled by setting the disableHixie option to true.)
• HyBi drafts 07-12 (Use the option protocolVersion: 8, or argument -p 8 for wscat)
• HyBi drafts 13-17 (Current default, alternatively option protocolVersion: 13, or argument -p 13 for wscat)

See the echo.websocket.org example below for how to use the protocolVersion option.

Usage

Installing

npm install ws

Sending and receiving text data

var WebSocket = require('ws');
var ws = new WebSocket('ws://www.host.com/path');
ws.on('open', function() {
    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() {
    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(ws) {
    ws.on('message', function(message) {
        console.log('received: %s', message);
    });
    ws.send('something');
});

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(error) {
    // if error is null, 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() {
    console.log('connected');
    ws.send(Date.now().toString(), {mask: true});
});
ws.on('close', function() {
    console.log('disconnected');
});
ws.on('message', function(data, flags) {
    console.log('Roundtrip time: ' + (Date.now() - parseInt(data)) + 'ms', flags);
    setTimeout(function() {
        ws.send(Date.now().toString(), {mask: true});
    }, 500);
});

wscat against echo.websocket.org

$ npm install -g ws
$ wscat -c ws://echo.websocket.org -p 8
connected (press CTRL+C to quit)
> hi there
< hi there
> are you a happy parrot?
< are you a happy parrot?

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.

Running the tests

make test

API Docs

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

License

(The MIT License)

Copyright (c) 2011 Einar Otto Stangvik <[e-mail]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.