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wBittorrent

A (very) basic BitTorrent client CLI written in C++. It implements from scratch parts of the BitTorrent protocol.

For now, it only supports downloading a single file from a single peer. It does not support seeding and it uses a naive strategy for piece selection (downloading pieces in order).

What it currently does:

• bencode
• .torrent file parsing
• peers discovery via tracker (HTTP)
• peer handshake and communication (TCP) for downloading pieces

Usage

./bittorrent info <torrent file>
./bittorrent peers <torrent file>
./bittorrent download_piece -o <output_file> <torrent file>
./bittorrent download -o <output_file> <torrent file>

Build

# building
cmake . -B build
cmake --build build

# building with tests and debug
cmake . -B build -DBUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Debug
cmake --build build --target test

Resources used

• BitTorrent protocol specification
• theory.org wiki BitTorrent page
• CodeCrafters BitTorrent challenge