Two players online ?

Hi!
I wrote (pure Java) a simple clone of the Kee Games tank game .It was a two players game , but i’m working in some very basic enemy AI.Meanwhile , i would like instead to play it online with a
friend .The problem is that the tutorials around are very complex and aimed to many players .
There is a simple way to solve my problem ?
Thanks in advance.
P.S.:
i have the basic networking knowledge you can find in every decent Java book
P.P.S.:
not to say that a simple tip like where to look is more than enough