Bittorrent.Umbrella

Bittorrent

A work in progress implementation of the BitTorrent Specification as a method to learn Elixir. Inspired by Building a BitTorrent client from the ground up in Go.

Usage

> mix escript.build
> ./bittorrent --path ./my.torrent --output ./my_torrents/

Working

• Parse a tracker file and use it to request peers from the tracker
• Connect to peers and handshake with them
• Record what pieces individual peers actually have
• Send requests for blocks
• Respect choke / unchoke
• Respect interested / not interested
• Save downloaded pieces to disk
• Dropped / timeout connection recovery
• Get working as a script
• Rearchitect focussing on one piece per peer
• Respond to requests for blocks (actually seed!)

To Do

• Re-announce to the tracker at a given interval
• Web UI for viewing torrent status
• Web UI for uploading a new torrent
• Assemble the pieces into an actual file
• Store pieces in ETS / DETS / Mnesia
• Listen for incoming connections
• Send have / cancel on completion of piece

Architecture

Bittorrent supervises one Bittorrent.Client, in charge of downloading the contents of a given .torrent file. It supervises N Bittorrent.PeerDownloader, who each are responsible for communications with a given peer.

Bittorrent.PeerDownloader does all of the following forever:

1. Fetching an available peer from the Client.
2. Once a peer is acquired use a Task to establish connection to this peer asynchronously.
3. Once a connection is established, fetch an available piece from the Client
4. Once a piece is acquired, use a Task to run the TCP socket loop between themselves and the peer, fetching blocks of the piece until is complete, and is reported back to the Client.
5. (Loop back to step 3)

Installation

If available in Hex, the package can be installed by adding bittorrent to your list of dependencies in mix.exs:

def deps do
  [
    {:bittorrent, "~> 0.1.0"}
  ]
end

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/bittorrent.