Introduction to Network multiplayer game in Java

Hello Friends, i want to know the best option i have to consider at the moment of make a online game, i mean, why do i have to know apart of:

TCP/UDP, networks, sockets, client, servers, etc, etc…
i want to focus only in a game, i have been reading a lots of tutorials but i still dont know how to move the player from the client to the server, o how to change the animation from one to another, i have a lot of information in my mind but i still dont link it.

so, there is anybody who know how to make it step by step, 1, and then 2 and then 3, im so confused about it…

thanks in advance, any link to tutorial, or article will be good received…

also i have been looking in this forum but the links are obsoletes and a few ones are working.