I built a BitTorrent-inspired distributed file sharing system in C++ to get hands-on with low-level networking and concurrency — a centralized tracker for peer discovery, with actual file transfers happening peer-to-peer over raw TCP sockets. Downloads are split into chunks and pulled in parallel across multiple peers using multithreading, with a rarest-first chunk selection strategy to keep transfers efficient even as peers come and go. I added SHA-1 integrity verification on every chunk and built user authentication with group-based sharing on top.

Skills demonstrated: C++, socket programming, POSIX APIs, multithreading/concurrency, distributed systems design, cryptographic integrity verification (SHA-1).