Doug Comer's "Internetworking with TCP IP" volumes 1&2. Walks you through the protocol suite along with the implementation of a simple stack in C.

https://www.cs.purdue.edu/homes/comer/netbooks.html

Richard Steven's "TCP/IP Illustrated" books are the original works, Unix network programming at its finest. More advanced than Comer's book, and much more applicable. Get used, older editions if cheaper, you will be fine.