BitTorrent Implementation in Go

This project is a BitTorrent protocol implementation in Go, aimed at providing essential components for torrent file management and peer-to-peer file sharing.

Prerequisites

• Go 1.18 or later

Installation

1. Clone the repository:

   git clone https://github.com/rishavmehra/bittorrent-v2.git
   cd bittorrent-v2
   
   

Features (To-Do)

• Bencode Decoder: Decode Bencoded data used in .torrent files.
• Parse .torrent File: Extract metadata from .torrent files, including file names, sizes, and piece information(Metainfo File Structure)
• Info Hash
• Piece Hashes: Generate and verify piece hashes to ensure data integrity during download.
• Tracker Request(find peers): Implement peer discovery methods to find other peers in the torrent swarm.
• Peers Handshake: Handle the initial handshake process between peers to establish connections.
• Download Piece: Download individual pieces of the file from peers.
• Full File: Assemble and save the complete file after all pieces have been downloaded.

https://binspec.ccio.dev/

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• Bencode Decoder https://wiki.theory.org/BitTorrentSpecification#Bencoding

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• Metainfo File Structure https://wiki.theory.org/BitTorrentSpecification#Metainfo_File_Structure

For example, here's the linuxmint-18.3-cinnamon-64bit.iso metainfo file, decoded:

iex> Metatorrent.decode(File.read! "linuxmint-18.3-cinnamon-64bit.iso.torrent")
%Metatorrent.Metainfo{
  announce: "https://torrents.linuxmint.com/announce.php",
  announce_list: [],
  nodes: [],
  comment: nil,
  created_by: "Transmission/2.84 (14307)",
  creation_date: ~U[2017-11-27 09:27:31Z],
  info: %Metatorrent.SingleFileInfo{
    length: 1899528192,
    md5sum: nil,
    name: "linuxmint-18.3-cinnamon-64bit.iso",
    piece_length: 1048576,
    pieces: [
      <<167, 53, 69, 58, 13, 103, 134, 251, 174, 104, 105, 210, 94, 112, 197, 52,
  205, 246, 155, 130>>,
      ...
    ]
  },
  info_hash: <<210, 229, 63, 182, 3, 101, 45, 153, 25, 145, 182, 173, 35, 87,
    167, 162, 132, 90, 83, 25>>
}

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• Trackers(Info Hash)
  info_hash -> urlencoded 20-byte SHA1 hash of the value of the info key from the Metainfo file. Note that the value will be a bencoded dictionary, given the definition of the info key above

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• Piece Hashes
  Piece length and piece hashes are specified in the info dictionary

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• Tracker Request(Find Peers) Detailed information
  • Tracker GET requests
    • info_hash: 20 bytes long, will need to be URL encoded - NOT the hexadecimal representation, which is 40 bytes long (we already calculated the info hash - above)
    • peer_id: A string of length 20 which this downloader uses as its id. Each downloader generates its own id at random at the start of a new download. This value will also almost certainly have to be escaped.
    • port: The port number this peer is listening on. Common behavior is for a downloader to try to listen on port 6881 and if that port is taken try 6882, then 6883, etc. and give up after 6889
    • uploaded: The total amount uploaded so far, encoded in base ten ascii.
    • downloaded: The total amount downloaded so far, encoded in base ten ascii.
    • left: The number of bytes this peer still has to download, encoded in base ten ascii.

http://bttracker.debian.org:6969/announce?compact=1&downloaded=0&info_hash=%1B%D0%88%EE%91f%A0b%CFJ%F0%9C%F9%97+%FAn%1A13&left=661651456&peer_id=%C1%935%12%CB+k%F7%9F~%90V%9F%BF%A4%D1%CF%065%EA&port=6881&uploaded=0

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• Peers Handshake