WebTorrent – Streaming torrent client for node & the browser

WebTorrent is a streaming torrent client that works in node.js and the browser. YEP, THAT'S RIGHT. The browser. It's written completely in JavaScript – the language of the web – so the same code works in both runtimes.

In browsers, WebTorrent uses WebRTC (data channels) for peer-to-peer transport. It can be used without browser plugins, extensions, or installations. It's Just JavaScript™.

Simply include the webtorrent.min.js script on your page to start fetching files over WebRTC using the BitTorrent protocol. See code examples below.

To make BitTorrent work over WebRTC (which is the only p2p transport that works on the web) we made some protocol changes. Currently, WebTorrent clients can only connect to other WebTorrent clients.

We hope established torrent clients (uTorrent, Transmission, Vuze, etc.) will add support for WebRTC and the WebTorrent extensions so they can swarm with peers from both the normal and web networks.

Warning: This is pre-alpha software. Watch/star to follow along with progress.

Features

• Torrent client for node.js & the browser (same npm module!)
• Insanely fast
• Streaming video to many devices (including AirPlay, Chromecast, and VLC player)
• Download multiple torrents simultaneously, efficiently
• Pure Javascript (no native dependencies)
• Exposes files as streams (and fetches pieces on-demand before torrent is finished
  • Fetches data from the network on-demand, so streaming and seeking are supported
  • Seamlessly switches between sequential and rarest-first piece selection strategy
• Supports advanced torrent client features
  • magnet uri support via ut_metadata
  • peer discovery via dht, tracker, and ut_pex
  • protocol extension api for adding new extensions
• Comprehensive test suite (completely offline, so it's reliable and fast)

Browser-specific features

• Uses WebRTC data channels for lightweight peer-to-peer communication (no plugins)
• No silos. WebTorrent is a P2P network for the entire web. WebTorrent clients running on one domain can connect to clients on any other domain.
• Stream video torrents into a <video> tag (webm (vp8, vp9) or mp4 (h.264))

Ways to help

• Join us in IRC on freenode at #webtorrent if you want to help with development, or you just want to hang out with some cool mad science hackers :)
• Create a new issue to report bugs
• Fix an issue. Note: WebTorrent is an OPEN Open Source Project!
• Donate bitcoin if you believe in the vision and wish to support the project. 1B6aystcqu8fd6ejzpmMFMPRqH9b86iiwh or Coinbase.

Install

With npm, run:

npm install webtorrent -g

Usage

WebTorrent is the first BitTorrent client that works in the browser, using open web standards (no plugins, just HTML5 and WebRTC)!

It's easy to get started!

In the browser

Download a file

Downloading a file is simple:

var WebTorrent = require('webtorrent')
var concat = require('concat-stream')

var client = new WebTorrent()

client.download(magnet_uri, function (torrent) {
  // Got torrent metadata!
  console.log('Torrent info hash:', torrent.infoHash)

  torrent.files.forEach(function (file) {
    // Get the file data as a Buffer (Uint8Array typed array)
    file.createReadStream().pipe(concat(function (buf) {

      // Append a link to download the file
      var a = document.createElement('a')
      a.download = file.name
      a.href = URL.createObjectURL(new Blob([ buf ]))
      a.textContent = 'download ' + file.name
      document.body.appendChild(a)
    }))
  })
}

Seed a file

Seeding a file is simple, too:

var dragDrop = require('drag-drop/buffer')
var WebTorrent = require('webtorrent')

var client = new WebTorrent()

// When user drops files on the browser, create a new torrent and start seeding it!
dragDrop('body', function (files) {
  client.seed(files, function onTorrent (torrent) {
    // Client is seeding the file!
    console.log('Torrent info hash:', torrent.infoHash)
  })
})

Browserify

WebTorrent works great with browserify, an npm module that let's you use node-style require() to organize your browser code and load modules installed by npm (as seen in the previous examples).

WebTorrent is also available as a standalone script (webtorrent.min.js) which exposes WebTorrent on the window object, so it can be used with just a script tag:

<script src="webtorrent.min.js"></script>

In node.js

WebTorrent also works in node.js, using the same npm module! It's mad science!

As a command line app

WebTorrent is available as a command line app Here's how to use it:

$ npm install webtorrent -g
$ webtorrent --help

To download a torrent:

$ webtorrent magnet_uri

$ webtorrent /path/to/file.torrent

To stream a torrent to a device like AirPlay or Chromecast, just pass a flag:

$ webtorrent magnet_uri --airplay

There are many supported streaming options:

  --airplay        stream to Apple TV (AirPlay)
  --chromecast     stream to Chromecast
  --mplayer        stream to MPlayer
  --mpv            stream to MPV
  --omx [jack]     stream to omx (jack=local|hdmi)
  --vlc            stream to VLC
  --xbmc           stream to XBMC

WebTorrent in production

• Instant – Secure, anonymous, streaming file transfer [code]
• Your app here! (send a PR or open an issue with the URL to your app)

API

This API should work exactly the same in node and the browser. Open an issue if this is not the case.

client = new WebTorrent([opts])

Create a new WebTorrent instance.

If opts is specified, then the default options (shown below) will be overridden.

{
  dht: true,         // Whether or not to enable DHT
  maxPeers: 100,     // Max number of peers to connect to (per torrent)
  nodeId: '',        // DHT protocol node ID (otherwise, randomly generated)
  peerId: '',        // Wire protocol peer ID (otherwise, randomly generated)
  storage: function  // custom storage engine, or false for in-memory engine
  tracker: true,     // Whether or not to enable trackers
  verify: true,      // Verify previously stored data before starting
}

client.add(torrentId, [opts], [function ontorrent (torrent) {}])

Start downloading a new torrent. Aliased as client.download.

torrentId can be one of:

• magnet uri (utf8 string)
• torrent file (buffer)
• info hash (hex string or buffer)
• parsed torrent (from parse-torrent)
• http/https url to a torrent file (string)
• filesystem path to a torrent file (string)

If ontorrent is specified, then it will be called when this torrent is ready to be used (i.e. metadata is available). Note: this is distinct from the 'torrent' event which will fire for all torrents.

If you want access to the torrent object immediately in order to listen to events as the metadata is fetched from the network, then use the return value of client.add. If you just want the file data, then use ontorrent or the 'torrent' event.

client.seed(input, [opts], [function onseed (torrent) {}])

Start seeding a new torrent.

input can be any of the following:

• path to the file or folder on filesystem (string)
• W3C File object (from an <input> or drag and drop)
• W3C FileList object (basically an array of File objects)
• Array of File objects

If opts is specified, it should contain the following types of options:

• options for create-torrent (to allow configuration of the .torrent file that is created)
• options for client.add (see above)

If onseed is specified, it will be called when the client has begun seeding the file.

client.on('torrent', function (torrent) {})

Emitted when a torrent is ready to be used (i.e. metadata is available and storage is ready). See the torrent section for more info on what methods a torrent has.

client.remove(torrentId, [function callback (err) {}])

Remove a torrent from the client. Destroy all connections to peers and delete all saved file data. If callback is specified, it will be called when file data is removed.

client.destroy()

Destroy the client, including all torrents and connections to peers.

client.listen([port], function () {})

Listen for incoming peers on the specified port. Port defaults to 6881

client.torrents[...]

An array of all torrents in the client.

client.get(torrentId)

Returns the torrent with the given torrentId. Convenience method. Easier than searching through the client.torrents array.

client.ratio

Seed ratio for all torrents in the client.

torrent api

torrent.files[...]

An array of all files in the torrent. See the file section for more info on what methods the file has.

torrent.swarm

The attached bittorrent-swarm instance.

torrent.remove()

Alias for client.remove(torrent).

torrent.addPeer(addr)

Adds a peer to the underlying bittorrent-swarm instance.

torrent.select(start, end, [priority], [notify])

Selects a range of pieces to prioritize starting with start and ending with end (both inclusive) at the given priority. notify is an optional callback to be called when the selection is updated with new data.

torrent.deselect(start, end, priority)

Deprioritizes a range of previously selected pieces.

torrent.critical(start, end)

Marks a range of pieces as critical priority to be downloaded ASAP. From start to end (both inclusive).

file api

file.name

File name, as specified by the torrent. Example: 'some-filename.txt'

file.path

File path, as specified by the torrent. Example: 'some-folder/some-filename.txt'

file.length

File length (in bytes), as specified by the torrent. Example: 12345

file.select()

Selects the file to be downloaded, but at a lower priority than files with streams. Useful if you know you need the file at a later stage.

file.deselect()

Deselects the file, which means it won't be downloaded unless someone creates a stream for it.

stream = file.createReadStream([opts])

Create a readable stream to the file. Pieces needed by the stream will be prioritized highly and fetched from the swarm first.

You can pass opts to stream only a slice of a file.

{
  start: startByte,
  end: endByte
}

Both start and end are inclusive.

Modules

Most of the active development is happening inside of small npm modules which are used by WebTorrent.

The Node Way™

"When applications are done well, they are just the really application-specific, brackish residue that can't be so easily abstracted away. All the nice, reusable components sublimate away onto github and npm where everybody can collaborate to advance the commons." — substack from "how I write modules"

Modules

These are the modules I am writing to make WebTorrent work:

module	tests	version	description
webtorrent			torrent client (this module)
addr-to-ip-port			cache for addr->ip:port
bittorrent-dht			distributed hash table client
bittorrent-peerid			identify client name/version
bittorrent-protocol			bittorrent protocol stream
bittorrent-swarm			bittorrent connection manager
bittorrent-tracker			bittorrent tracker server/client
buffer			node buffer api for the browser
create-torrent			create .torrent files
ip-set			efficient mutable ip set
load-ip-set			load ip sets from local/network
magnet-uri			parse magnet uris
parse-torrent			parse torrent identifiers
parse-torrent-file			parse .torrent files
simple-peer			simpler webrtc api
simple-websocket			simpler websocket api
string2compact			convert 'hostname:port' to compact
torrent-discovery			find peers via dht and tracker
typedarray-to-buffer			efficient buffer creation
ut_metadata			metadata for magnet uris (ext)
ut_pex			peer discovery (ext)
webtorrent-swarm			webtorrent connection management
webtorrent-tracker			webtorrent tracker server/client

Todo

• compress-sdp (compress sdp messages to lighten load on webtorrent trackers & dht)
• protocol extension: protocol encryption
• protocol extension: µTP
• protocol extension: UPnP and NAT-PMP port forwarding
• protocol extension: webseed support
• webtorrent-dht

Contribute

WebTorrent is an OPEN Open Source Project. Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit.

WebTorrent is only possible due to the excellent work of the following contributors:

Feross Aboukhadijeh	GitHub/feross	Twitter/@feross
Daniel Posch	GitHub/dcposch	Twitter/@dcposch
John Hiesey	GitHub/jhiesey	Twitter/@jhiesey
Travis Fischer	GitHub/fisch0920	Twitter/@fisch0920
Astro	GitHub/astro	Twitter/@astro1138
Iván Todorovich	GitHub/ivantodorovich	Twitter/@ivantodorovich
Mathias Buus	GitHub/mafintosh	Twitter/@mafintosh
Bob Ren	GitHub/bobrenjc93	Twitter/@bobrenjc93

Clone the code

git clone https://github.com/feross/webtorrent.git
cd webtorrent
npm install
./bin/cmd.js --help

Enable debug logs

In node, enable debug logs by setting the DEBUG environment variable to the name of the module you want to debug (e.g. bittorrent-protocol, or * to print all logs).

DEBUG=* webtorrent

Of course, this also works for the development version:

DEBUG=* ./bin/cmd.js

In the browser, enable debug logs by running this in the developer console:

localStorage.debug = '*'

Disable by running this:

localStorage.removeItem('debug')

Clone all dependencies

WebTorrent is a modular BitTorrent client, so functionality is split up into many npm modules. You can git clone all the relevant dependencies with one command. This makes it easier to send PRs:

./bin/clone.sh

Talks about WebTorrent

• Sep 2014 (NodeConf EU) – WebTorrent & WebRTC: Mad Science (first working demo of WebTorrent)
• May 2014 (JS.LA) – How I Built a BitTorrent Client in the Browser (progress update; node client working)
• Oct 2013 (RealtimeConf) – WebRTC Black Magic (RealtimeConf) (where I first shared the idea of WebTorrent)

Known issues

Downloads don't start on Chromebook

Chromebooks are set to refuse all incoming connections by default. To change this, run:

sudo iptables -P INPUT ACCEPT

License

MIT. Copyright (c) Feross Aboukhadijeh.