Network socket programming is a little low level for what most people do with Mathematica. You likely aren't going to find a tutorial on this and it'd would be a bad way to get started learning Mathematica. Making a webserver isn't a good starting project for this language.
If you haven't already, take a quick look at the virtual book. This will give a good understanding of how Mathematica works and what kinds of tasks it's often used for:
http://reference.wolfram.com/mathematica/howto/UseTheVirtualBook.htmlIf you're a programmer who wants a more principle-based introduction to the wolfram language, I'd reccomend
http://www.mathprogramming-intro.org