1.0.0 • Public • Published

DataChannel.js : A JavaScript wrapper library for RTCDataChannel APIs / Demos

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npm install datachannel

# or
bower install datachannel

DataChannel.js is a JavaScript library useful to write many-to-many i.e. group file/data sharing or text chat applications. Its syntax is easier to use and understand. It highly simplifies complex tasks like any or all user rejection/ejection; direct messages delivery; and more.

If you want all DataChannel.js functionalities along with media streaming and runtime additions/deletions then RTCMultiConnection.js is a good chose with similar APIs/syntax.


  1. Direct messages � to any user using his user-id
  2. Eject/Reject any user � using his user-id
  3. Leave any room (i.e. data session) or close entire session using leave method
  4. File size is limitless!
  5. Text message length is limitless!
  6. Size of data is also limitless!
  7. Fallback to firebase/
  8. Users' presence detection using onleave
  9. Latency detection
  10. Multi-longest strings/files concurrent
  11. File queue support added. Previously shared files will be auto transmitted to each new peer.

Demos using DataChannel.js

  1. DataChannel basic demo
  2. Auto Session Establishment and Users presence detection
  3. Text Chat using Pusher and DataChannel.js

Try a Quick Demo (Text Chat)

<script src="//"> </script> 
<button id="setup-datachannel" style="width:30%;">Open NEW DataChannel</button>
<input type="text" id="chat-input" disabled style="font-size: 2em; width: 65%;"><br />
<div id="chat-output"></div>
var chatOutput = document.getElementById('chat-output');
var chatInput = document.getElementById('chat-input');
chatInput.onkeypress = function (e) {
    if (e.keyCode != 13) return;
    chatOutput.innerHTML = 'Me: ' + this.value + '<hr />' + chatOutput.innerHTML;
    this.value = '';
var channel = new DataChannel();
channel.onopen = function (userid) {
    chatInput.disabled = false;
    chatInput.value = 'Hi, ' + userid;
channel.onmessage = function (message, userid) {
    chatOutput.innerHTML = userid + '' + message + '<hr />' + chatOutput.innerHTML;
channel.onleave = function (userid) {
    chatOutput.innerHTML = userid + ' Left.<hr />' + chatOutput.innerHTML;
// search for existing data channels
document.querySelector('button#setup-datachannel').onclick = function () {
    // setup new data channel;

First Step: Link the library

<script src="//"></script>

Last Step: Start using it!

var channel = new DataChannel('[optional] channel-name');
channel.send(file || data || 'text-message');

open/connect data channels

// to create/open a new channel'channel-name');
// if someone already created a channel; to join it: use "connect" method

onopen and onmessage

If you're familiar with WebSockets; these two methods works in the exact same way:

channel.onopen = function(userid) { }
channel.onmessage = function(message, userid, latency) { }

user-ids can be used to send direct messages or to eject/leave any user:


Allows you show list of all available data channels to the user; and let him choose which one to join:

channel.ondatachannel = function(data_channel) {
    // or
        owner: data_channel.owner
    // id:    unique identifier for the session
    // owner: unique identifier for the session initiator

Use custom user-ids

channel.userid = 'predefined-userid';

Remember; custom defined user-id must be unique username.

Direct messages

channel.channels[userid].send(file || data || 'text message');

Eject/Reject users using their user-ids

channel.eject(userid);  // throw a user out of your room!

Close/Leave the entire room

channel.leave();        // close your own entire data session

Detect users' presence

channel.onleave = function(userid) { };

Auto Close Entire Session

When room initiator leaves; you can enforce auto-closing of the entire session. By default: it is false:

channel.autoCloseEntireSession = true;

It means that session will be kept active all the time; even if initiator leaves the session.

You can set autoCloseEntireSession before calling leave method; which will enforce closing of the entire session:

channel.autoCloseEntireSession = true;
channel.leave(); // closing entire session

uuid for files

You can get uuid for each file (being sent) like this:

var uuid = file.uuid; // "file"-Dot-uuid

To Share files

var progressHelper = {};
// to make sure file-saver dialog is not invoked.
channel.autoSaveToDisk = false;
channel.onFileProgress = function (chunk, uuid) {
    var helper = progressHelper[chunk.uuid];
    helper.progress.value = chunk.currentPosition || chunk.maxChunks || helper.progress.max;
    updateLabel(helper.progress, helper.label);
channel.onFileStart = function (file) {
    var div = document.createElement('div');
    div.title =;
    div.innerHTML = '<label>0%</label> <progress></progress>';
    appendDIV(div, fileProgress);
    progressHelper[file.uuid] = {
        div: div,
        progress: div.querySelector('progress'),
        label: div.querySelector('label')
    progressHelper[file.uuid].progress.max = file.maxChunks;
channel.onFileSent = function (file) {
    progressHelper[file.uuid].div.innerHTML = '<a href="' + file.url + '" target="_blank" download="' + + '">' + + '</a>';
channel.onFileReceived = function (fileName, file) {
    progressHelper[file.uuid].div.innerHTML = '<a href="' + file.url + '" target="_blank" download="' + + '">' + + '</a>';
function updateLabel(progress, label) {
    if (progress.position == -1) return;
    var position = +progress.position.toFixed(2).split('.')[1] || 100;
    label.innerHTML = position + '%';

File Queue

File Queue support added to make sure newly connected users gets all previously shared files.

You can see list of previously shared files:

console.log( channel.fileQueue );

Auto-Save file to Disk

By default; autoSaveToDisk is set to true. When it is true; it will save file to disk as soon as it is received. To prevent auto-saving feature; just set it false:

channel.autoSaveToDisk = false; // prevent auto-saving!
channel.onFileReceived = function (fileName, file) {
    // file.url
    // file.uuid
    hyperlink.href = file.url;

Latency Detection

channel.onmessage = function(message, userid, latency) {
    console.log('latency:', latency, 'milliseconds');

Concurrent Transmission

You can send multiple files concurrently; or multiple longer text messages:

// individually
// or as an array
channel.send([fileNumber1, fileNumber2, fileNumber3]);
channel.send('longer string-1');
channel.send('longer string-2');
channel.send('longer string-3');

Errors Handling

// error to open data ports
channel.onerror = function(event) {}
// data ports suddenly dropped
channel.onclose = function(event) {}

Data session direction

Default direction is many-to-many.

channel.direction = 'one-to-one';
channel.direction = 'one-to-many';
channel.direction = 'many-to-many';


For signaling; please check following page:

Remember, you can use any signaling implementation that exists out there without modifying any single line! Just skip below code and open above link!


  1. Video Presentation for openSignalingChannel:
  2. Documentation for openSignalingChannel:

Use your own for signaling

dataChannel.openSignalingChannel = function(config) {
   var channel = || || 'default-channel';
   var socket = io.connect('/?channel=' + channel); = channel;
   socket.on('connect', function () {
      if (config.callback) config.callback(socket);
   socket.send = function (message) {
        socket.emit('message', {
            sender: dataChannel.userid,
            data  : message
   socket.on('message', config.onmessage);

Use Pusher for signaling

A demo & tutorial available here:

Another link:

Use firebase for signaling

// firebase stores data on their servers
// that's why transmitting room once
// unlike other signalling gateways; that
// doesn't stores data on servers.
channel.transmitRoomOnce = true;
channel.openSignalingChannel = function (config) {
    channel = || || 'default-channel';
    var socket = new window.Firebase('' + channel); = channel;
    socket.on('child_added', function (data) {
        var value = data.val();
        if (value == 'joking') config.onopen && config.onopen();
        else config.onmessage(value);
    socket.send = function (data) {
    this.socket = socket;
    return socket;

Other Signaling resources

  1. XHR for Signaling
  2. WebSync for Signaling
  3. SignalR for Signaling
  4. Pusher for Signaling
  5. Firebase for Signaling
  6. PubNub for Signaling


transmitRoomOnce is preferred when using Firebase for signaling. It saves bandwidth and asks DataChannel.js library to not repeatedly transmit room details.

channel.transmitRoomOnce = true;

Browser Support

DataChannel.js works fine on following browsers:

Browser Support
Firefox Stable / Aurora / Nightly
Google Chrome Stable / Canary / Beta / Dev
Android Chrome Beta


DataChannel.js is released under MIT licence . Copyright (c) Muaz Khan.

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