WebTorrent - Streaming torrent client for node and the browser

Warning: This is pre-alpha software. Nothing works yet. Watch/star to follow along with progress.

Ways to help

• Donations. I fight for the users. JavaScript and WebRTC are my sword and shield. I'm working on WebTorrent almost every night so please support me if you believe in the vision. Send bitcoin to 1B6aystcqu8fd6ejzpmMFMPRqH9b86iiwh or donate via Coinbase.
• Fix bugs, add features. Join #webtorrent on Freenode. Take a look at the open issues and see what you can help with.

Here's how to get started:

git clone https://github.com/feross/webtorrent.git
cd webtorrent
npm install
npm start

Planned Features

• BitTorrent in your browser!
• No plugins (uses WebRTC Data Channels for peer-to-peer data)
• Streaming playback (get first pieces first)
  • Into video tag with MediaSource API when possible
  • Flash player with JS bridge for other media types
• Works with .torrent files and magnet links
• Supports DHT (trackerless torrents) over WebRTC
  • Extensions to DHT protocol to work over WebRTC
  • DHT nodes do "peer introductions" so WebRTC can work without a centralized signaling server
• Supports completely serverless, trackerless operation

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.

NPM Modules

Most of the active development is happening inside of smaller npm modules which will be used by WebTorrent. These are the modules I am writing to make WebTorrent work:

Targets:

• webtorrent.app (bittorrent client for os x, windows & linux)
• webtorrent (bittorrent client for node.js)
• webtorrent-chrome (bittorrent client for chrome -- on hold)
• webtorrent.js (bittorrent client for the web -- coming soon)

Modules:

• bittorrent-client (streaming torrent engine)
• bittorrent-dht (dht client)
• bittorrent-peerid (peer id -> client name/version)
• bittorrent-protocol (protocol stream)
  • extension: ut_metadata (fetch metadata for magnet uris)
  • extension: ut_pex (peer discovery protocol)
  • extension: encryption
  • extension: µTP
  • extension: UPnP and NAT-PMP port forwarding
  • extension: webseed support
• bittorrent-swarm
• bittorrent-tracker
• buffer
• create-torrent
• magnet-uri
• parse-torrent
• string2compact
• typedarray-to-buffer
• compress-sdp
• webtorrent-bootstrap
• webtorrent-dht
• webtorrent-protocol
• webtorrent-swarm
• webtorrent-verifier
• webworker-pool

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"

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)

Todo for basic bitorrent client as node.js command line app

• Use UDP/TCP APIs
• Support DHT
• Support peer wire protocol
• Support magnet links (fetching .torrent from network)
• Basic UI
• Fetching logic
• Large file saving (downloading in-memory for now, later IndexedDB/FileSystem API)
• Streaming video
  • HTTP stream to VLC, like peerflix

Todo for webtorrent

• DHT over WebRTC (add new method for peer introduction)
  • Use bootstrap server for initial introduction
  • POST endpoint for sending offer/getting answer
• Easy torrent creation
• UPnP or NAT-PMP (so the hybrid client can get listed in peers' routing tables)
• Streaming video
  • MediaSource into video tag
  • Flash player for other media types

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

Talks about WebTorrent

• WebTorrent: Bringing BitTorrent to the Web with WebRTC (CraftConf) (April 2014, progress update on WebTorrent)
• WebRTC Black Magic (RealtimeConf) (October 2013, where I first shared the idea for WebTorrent (skip to end for WebTorrent))

License

MIT. Copyright (c) Feross Aboukhadijeh.