small project C

https://github.com/thetr4/tcplinserv

I wrote this when I was 15 (I had some programming experience before). I'm 16 now and I'm stumped when it comes to programming. I understand the problem is that it only accepts one connection, and it's not even a chat. It's kind of an experimental project; I was just curious, so I did it.

What recommendations would you offer me?