BitTorrent in Python

This BitTorrent program implements various functionalities for handling magnet links and torrent files, including downloading pieces, parsing magnet links, and peer communication using the Bittorrent Peer Protocol.

Prerequisites

• Python 3.11+
• Pipenv

  pip install pipenv
  
  # Check if correctly installed
  pipenv --version

Table of Contents

• Setup
• Commands

Setup

1. Clone the repository and ensure you have the necessary dependencies installed.

   git clone https://github.com/sourasishbasu/bittorrent-python.git
   cd bittorrent-python/

2. Set up a Python virtual environment and install packages with pipenv:

   pipenv install
   pipenv shell

Usage

You can run the program using the following command:

./your_bittorrent.sh <command> [options]

Note

Switch to python app/main.py instead of ./your_bittorrent.sh if executing on Windows

Libraries Used

• bencode.py - To parse, decode and encode bencode format data
• urllib - Parsing magnet links
• requests - Sending GET requests to the torrent trackers
• Standard Libraries
  • socket
  • sys
  • os
  • hashlib
  • struct

Commands

magnet_handshake

• Description: Initiates a handshake with a peer using a magnet link announcing extension support.

• Parameters:

  • magnet_link: The magnet link to use for the handshake.

• Example:

  ./your_bittorrent.sh magnet_handshake "magnet:?xt=urn:btih:c5fb9894bdaba464811b088d806bdd611ba490af&dn=magnet3.gif&tr=http%3A%2F%2F127.0.0.1:38961%2Fannounce"

• Expected Output:

  Peer ID: 566d0e67e53794c815501f6b0eab681505d9e40b
  

magnet_parse

• Description: Parses a magnet link and extracts its components.

• Parameters:

  • magnet_link: The magnet link to parse.

• Example:

  ./your_bittorrent.sh magnet_parse "magnet:?xt=urn:btih:3f994a835e090238873498636b98a3e78d1c34ca&dn=magnet2.gif&tr=http%3A%2F%2Fbittorrent-test-tracker.codecrafters.io%2Fannounce"

• Expected Output:

  Tracker URL: http://bittorrent-test-tracker.codecrafters.io/announce
  Info Hash: 3f994a835e090238873498636b98a3e78d1c34ca

download

• Description: Downloads the entire file from the specified torrent.

• Parameters:

  • -o <output_file>: The path where the downloaded file will be saved.
  • <torrent_file>: The path to the torrent file.

• Example:

  ./your_bittorrent.sh download -o /tmp/torrents4241288447/congratulations.gif /tmp/torrents4241288447/congratulations.gif.torrent

• Expected Output:

  Total pieces: 4
  Downloading piece_0...
  Downloaded piece_0 at path: /tmp/test-0
  Downloading piece_1...
  Downloaded piece_1 at path: /tmp/test-1
  Downloading piece_2...
  Downloaded piece_2 at path: /tmp/test-2
  Downloading piece_3...
  Downloaded piece_3 at path: /tmp/test-3

download-piece

• Description: Downloads a specific piece of a file from a torrent.

• Parameters:

  • -o <output_file>: The path where the downloaded piece will be saved.
  • <torrent_file>: The path to the torrent file.
  • <piece_index>: The index of the piece to download.

• Example:

  ./your_bittorrent.sh download_piece -o /tmp/torrents2844170027/piece-0 /tmp/torrents2844170027/codercat.gif.torrent 0

• Expected Output:

  Downloaded piece_0 at path: /tmp/torrents2844170027/piece-0

handshake

• Description: Performs a peer handshake using the specified torrent file.

• Parameters:

  • <torrent_file>: The path to the torrent file.
  • <peer_address>: The socket address of the peer to connect to in the form of ip:port

• Example:

  ./your_bittorrent.sh handshake /tmp/torrents768971451/test.torrent 127.0.0.1:38919

• Expected Output:

  Peer ID: 9f07666979b5f02517d3edcb067abfd51a64ff6c

peers

• Description: Retrieves a list of peers' addresses from the tracker specified in the torrent file.

• Parameters:

  • <torrent_file>: The path to the torrent file.

• Example:

  ./your_bittorrent.sh peers /tmp/torrents3086496673/test.torrent

• Expected Output:

  Peers for test.torrent:
  
  188.119.61.177:6881
  185.107.13.235:54542
  88.99.2.101:6881

info

• Description: Retrieves information from a torrent file, including the tracker URL, length, and piece hashes.

• Parameters:

  • <torrent_file>: The path to the torrent file.

• Example:

  ./your_bittorrent.sh info /tmp/torrents1294332965/test.torrent

• Expected Output:

  Tracker URL: http://bttracker.debian.org:6969/announce
  Length: 1572864
  Info Hash: 753da4379d9a11139c55fecdba516f42dd9b1035
  Piece Length: 262144
  Piece Hashes:
  311c3f2436c1394acea2dafd2c812b7a3f4cd05a
  008c19a3468bef54e1a75e8b6a71d8529a1c0a6a
  912be9466cf461594129f6faf070a5aa6ca6b4d7
  f68259b74092c7a95965bdf0101f7a74110ca8f7
  d629b0e5245e67a3108598ef45f3be134d6837b7
  70edcac2611a8829ebf467a6849f5d8408d9d8f4
  

Roadmap

• feat: Download from magnet links

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