I think Beej's Guide to Network Programming is IMO hands down the best resource I've come across: https://beej.us/guide/bgnet/

It also doubles as a very great introduction to C, if that something you're interested in. It's funny because both C and socket level programming are often a barrier, or at least they were for me. It's an attestant to the quality of Beej's guide that he introduces both simultaneously, and makes it very approachable.

This is one of those sources that helped me disproportionately grow as a programmer in a short period of time.