ToyBitTorrent

This is a "Toy" implementation of BitTorrent built with Python3 and asyncio The client is not a practical BitTorrent client as it lacks too many features to really be useful. This project was created for my graduate networking class and to learn more about BitTorrent as well as Python's asyncio library.

Current features:

• [x] Download pieces (leeching)
• [x] Contact tracker periodically
• [X] Seed (upload) pieces
• [ ] Support multi-file torrents
• [ ] Resume a download

Getting started

Install pipenv for virtual enviornment

$ pip install pipenv
            

Install the needed dependencies

$ pipenv install
            

This client requires a file to be shares (can be anything) and its torrent file. Every torrent file has a tracker server field which is used to hold the IP address of the tracker server. This server lists all the availible seeders for a given file. The IP must be specified as: http://IP:PORT/announce

Design considerations

The pieces are all requested in order, not implementing a rarestfirst algorithm, and the pieces are all kept in memory until the entire torrent is downloaded.

Code walkthrough

trackerServer is run by the server for a given torrent file. It listens for connections from other seeder or leecher clients and keeps a list of all peers a seeder can leech from.

ToyBitTorrentClient is the center piece, it:

• Connects to the tracker in order to receive the peers to connect to.

• Based on that result, creates a Queue of peers that can be connected to.

• Determine the order in which the pieces should be requested from the remote peers.

• Assigns seeders to leecher roles once downloads are completed

Torrent is a custom class that holds all the torrent file information

For a tracker server, the commands are

$ pipenv run python3 trackerServer --t (torrentFileName)
            

For a seeder client,

$ pipenv run python3 startClient --t (torrentFileName) --f (fileName)
            

For a leecher client,

$ pipenv run python3 startClient --t (torrentFileName)
            

Commands should be ran in this order, as there needs to first be a tracker server to keep track of all peers and there must also first be a seeder for a leecher to download from.

Included are sample files that can be used to test the client. Transmission on MacOS was used to create the torrent files for both moby.txt and moby.jpg. New torrent files must be created since the tracker server IP addresses in these torrent files may be different from the IP address that will be ran locally.

References

Eliasson, M. (2016, August 24). A BitTorrent client in Python 3.5. Retrieved November 3, 2019,

• https://markuseliasson.se/article/bittorrent-in-python/

Cohen, B. (2008, January 10). The BitTorrent Protocol Specification. Retrieved November 3, 2019

• http://bittorrent.org/beps/bep_0003.html