From Book Description:

Beej's Guide to Network Programming has been one of the top socket programming guides on the Internet for the last 15 years, and it's now for the first time available as a lovingly bound paperback book! The Guide is designed to irreverently ease your first steps into Internet Sockets programming in C. Starting from the ground up, it provides complete examples of simple clients and servers supporting both IPv6 and IPv4. Once you get through the tutorial section of the book, Part Two contains a handy-dandy reference section which helps prevent the book from becoming simple dead weight on your shelf once you've devoured it.

The book focuses on the C programming language in Unix-like environments, but Windows users can still glean relevant information from its pages. Also, once you understand socket programming in C, you'll much more easily understand it in many other languages as well.