If you're using GCC, type 'man Socket' and it will tell you all about it. If you're using Visual C++ (how lame) there should be online help for WinSock. (It's almost the same). A quick google on "WinSock API" will get you tons of links like this:

http://burks.brighton.ac.uk/burks/pcinfo/progdocs/winsock/winsock.htm

oh, and thanks for the link.

and where do i type "man Socket"? in google? il try that btw.. so u dont need to answer if thats the answer

Nothing of course, but actually I thought about doing some networking code in C myself.
Not because it's better, but because it's a little more difficult to decompile and hack than a java class. Which I thought might help a little making for example a high score server 'cheater-unfriendly'.
But, I also found that this is just complicating development and it hardly helps anything as there are ways to complicate hacking in java too that work just as well. Probably better even.

NEVER rely on Security through obscurity - It just won't work (tm)

just to barging in

had any problems with cheaters then?

hmm... i'm not sure if that would help at all. most ppl wont decompile it. the more usual (generic) approach is sniffing, reverse the data structure and sending an own build packet to the server.

as long as u dont use encryption it's way too easy :>

and demotivating doesnt really work this way - if its harder it's just a bit more fun

www.try2hack.nl <- try it. it's fun =)

Do you know how to ping?

You must know the users IP address and then "ping" that address. If test packets are not returned, user is behind firewall/ or unavailable.

I've seen this at least in couple of books.

yeah i want the application on the users computer to beable to detect if the user is online, and then when he goes online to perform the work that must be done online.

ill give it a shot