What Should I Know to Start Network Programming in C++?

Hello, dear null-byte readers.

I am quite comfortable with the usage of C++, and I wish to start network programming. I've been learning about low level networking, yet I do not believe that I am on the right course. I would appreciate it if someone were to tell me what it is I need to know to start networking using C++. Also, I am looking for a powerful, high-level, user friendly and well documented library for C++ networking. I've been searching, and the most popular one seems to be the Boost:Asio library, yet there is no good documentation nor tutorials available. Thank you in advance.