WebTorrent – Streaming torrent client for node & the browser

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

Features

• Torrent client for node.js & the browser (same module!)
• Insanely fast
• Many streaming options (including AirPlay, Chromecast, VLC, browser <video> tag, and more)
• 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
  • awesome extension api for adding new extensions
• Comprehensive test suite (completely offline, so it's reliable and fast)
• Modular design (see module list)

Web-specific features

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

Ways to help

• Report bugs!
• Fix an open issue in this repo or one of it's many dependencies. WebTorrent is an OPEN Open Source Project!
• If you believe in the vision, send bitcoin to 1B6aystcqu8fd6ejzpmMFMPRqH9b86iiwh or donate via Coinbase to support the project.

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 :)

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!

Here's how to get started:

$ 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

API

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 any of the following:

• info hash (as a hex string or Buffer)
• magnet uri (as a utf8 string)
• .torrent file (as a 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			bittorrent dht 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
magnet-uri			parse magnet uris
parse-torrent			parse torrent identifiers
parse-torrent-file			parse .torrent files
simple-peer			webrtc wrapper api
simple-websocket			websocket wrapper api
string2compact			convert 'hostname:port' to compact
torrent-discovery			find peers via dht and tracker
typedarray-to-buffer			efficient buffer creation
ut_metadata			get 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.

Contributors

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

Enable debug output by setting the DEBUG environment variable to the name of the module you want to debug (e.g. bittorrent-tracker, or * to print all logs).

DEBUG=* ./bin/cmd.js

This even works for WebTorrent releases installed with npm install webtorrent -g:

DEBUG=* webtorrent

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)

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)

Project Goal

Build a browser BitTorrent client that requires no install (no plugin/extension/etc.) and fully-interoperates with the regular BitTorrent network. Use WebRTC Data Channels for peer-to-peer transport.

Since WebTorrent is web-first, it's simple for users who do not understand .torrent files, magnet links, NATs, etc. By making BitTorrent easier, it will be accessible to new swathes of users who were previously intimidated, confused, or unwilling to install a program on their machine to participate.

Interoperability with BitTorrent

Problem: WebTorrent clients and normal BitTorrent clients cannot directly connect because WebRTC cannot open UDP/TCP sockets. This is a security restriction on WebRTC that is unlikely to change. So, how do we get content into the WebTorrent network?

Best solution: Mainstream BitTorrent clients add support for WebTorrent. Basically, normal clients implement WebRTC so that WebTorrent clients can directly connect to them. (This could happen once WebTorrent has a lot of users.)

Good solution: Users who want to download torrents that aren't yet seeded by any WebTorrent users need to install a "hybrid client" that implements WebTorrent and BitTorrent. This can be implemented as a native torrent client that bridges the two networks like this:

• Hybrid clients can seed+leech from both WebTorrent and BitTorrent users.
• Hybrid clients are DHT nodes in both the WebTorrent and BitTorrent DHTs.
• The first time a hybrid client downloads a torrent that no other WebTorrent clients are seeding, they become the first WebTorrent seeder. (They essentially "bring" the file into the WebTorrent network).
• Important note: Hybrid clients never download torrents on behalf of other users. That would be a terrible idea.
• Until BitTorrent clients support WebTorrent, "pure" WebTorrent clients can only download from other WebTorrent clients.

WebTorrent vs BitTorrent

• WebTorrent is slower at finding peers since "DHT over WebRTC" requires multiple roundtrips for peer introductions. (This is a requirement of WebRTC signaling - no way around this)
• WebTorrent peers must keep their browser tab open to seed (Show UI to encourage seeding back at least 2x)
• Slower piece verification (SHA1) (max 2MB/s with web worker pool, Web Crypto API will bring huge speed-up when it's finally ready)
• WebTorrent bootstrap DHT node does a bit more work than a BitTorrent one since it must do WebRTC signaling. (Not a huge deal)

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.