What does HackerNews think of qBittorrent?

qBittorrent BitTorrent client

Language: C++

#15 in C++
FWIW, qbittorrent also has a built-in web interface. It's also one of the most feature-rich BitTorrent clients.

https://github.com/qbittorrent/qBittorrent

qBittorret has always been a bit cutting edge with Qt feature usage, which can be interesting.

https://github.com/qbittorrent/qBittorrent

not able to comment on code quality.

Paying isn't enough to get what you paid for, so...

https://github.com/SickChill/SickChill - automatically download TV episodes (about Linux)

https://github.com/CouchPotato/CouchPotatoServer - automatically download Movies (about Linux)

https://github.com/qbittorrent/qBittorrent - torrent client for downloading your Linux tv/movies...

You can start by going through the docs of popular open source bit-torrent clients like qBittorrent (https://github.com/qbittorrent/qBittorrent) or Transmission (https://github.com/transmission/transmission).

Join the respective IRCs on freenode, observe the chats and ask specific questions when you don't understand something and Google can't give you good answers.