A really good way to learn about concurrency is to write a SOCKS5 proxy. Start with a simple one using Python threads, then Python asyncio, and if you're brave

A really good way to learn about concurrency is to write a SOCKS5 proxy. Start with a simple one using Python threads, then Python asyncio, and if you're brave C sockets with poll/select. The C parts are in Beej's guide to network programming. The SOCKS5 spec is very simple and has an RFC.