[testouts]

https://bramcohen.livejournal.com/4563.html ... the founder of bittorent.

Ill add a personal note. Being a good professional programmer is also about understanding the context of your program. You will not always have the time to optimize for performance. You will not always have the time to refactor functionality to make it more modular for further variety. Sometimes you will need to skip test becuase deadline says it should be done yesterday. Learn to not be emotionally tied to the code. Get your job done, to the best quality you can for the time you have allotted. Dont be made if its not perfect. But during the train ride or in the shower think about how to make it better. This process of just grasping with the ideas of clean code are good training for when you have to approach a similar problem on the fly.

[Mizza]

That post is more about the architecture of the BitTorrent network than the original BitTorrent client.

As somebody has a built on top of the original BT codebase, it is not a well structured large program, and there is a reason nobody uses it for anything anymore.