💾 Peer-to-Peer File Sharing with BitTorrent

Implement a simplified BitTorrent-style file sharing protocol. Each peer stores and exchanges file chunks.

Validation Checklist:

• Upload a file and download it completely using chunk exchange
• Log peer join/leave and chunk ownership updates
• Visualize download progress per peer

BitTorrent Architecture

Running the System

1. Start the Tracker

python -m tracker.server

This starts the tracker on port 8080.

Check it's running with:

curl http://localhost:8080/health
# → {"status": "ok"}

2. Start the Seeder(s)

python -m seed.seed \
  -t path/to/your-file.torrent \
  -p 6881

This will:

• Parse the .torrent
• Announce to the tracker
• Serve pieces to requesting peers

3. Run the Client

To download the file using the BitTorrent client:

python -m client.main \
  -t path/to/your-file.torrent \
  -o path/to/output-file \
  -p 6889

• -t – path to the .torrent file
• -o – where to save the downloaded file (optional)
• -p – port to announce to tracker (should differ from seeder)

Project Structure

bittorrent/
├── handshake/
│   └── handshake.py         # Peer-to-peer handshake logic
├── leech/
│   └── leech.py             # Leech (downloading peer) implementation
├── msg/
│   └── message.py           # BitTorrent message definitions and handling
├── p2p/
│   └── p2p.py               # Core integration of P2P logic
├── seed/
│   └── seed.py              # Seeder (uploading peer) implementation
├── torrentfile/
│   └── torrentfile.py       # .torrent parsing and file download helpers
├── tracker/
│   ├── server.py            # FastAPI tracker server (announce endpoint)
│   └── models.py            # Data models for requests and peer info
├── utils/
│   ├── bitfield.py          # Efficient bitfield structure for piece availability
│   └── encoding.py          # Peer host/port serialization (compact format)
└── main.py                  # Project entry point (CLI or orchestrator)

References

• The BitTorrent Protocol Specification
• Building a BitTorrent client from the ground up