[JJMcJ]

Not really a full overview but a nice intro that covers much of what is done day to day, maybe most of it for a basic client or straightforward low capacity server:

http://beej.us/guide/bgnet/

[tptacek]

Julia Evans wrote something great about this, as she always does:

https://jvns.ca/blog/2014/08/12/what-happens-if-you-write-a-...