Port Scanner
A TCP port scanner written in C#, built to understand sockets from the bottom up.
An early project: a multi-threaded TCP port scanner in C#. Written to understand what a socket actually is rather than to be used.
It taught me more about concurrency than any tutorial did — connection timeouts, thread-pool exhaustion and the difference between a closed port and a filtered one are all things you learn quickly when your own scanner hangs.