Search for tutorials on using Sockets and SocketServers. I'd give you a link to one I have bookmarked but I seem to currently be locked out of my own desktop.

check my other post

http://www.daniweb.com/techtalkforums/post269569-4.html

Hi all i have a one big problem. How to do messenger server ? ! . I'm not sure using thread becouse thread is limited and performance ! Please help you solution

do your own homework, thread hijacker.

Edited: Oh, I didn't realize earlier that this thread was as old one.

I'd done PC to PC IM earlier. For that, you'll have to use socket programming, multi threading, exception handling and AWT. If you know all these topics, then post your specific problem and you'll get help.

So, question on the connection... Since I imagine sockets in java just send plain text, what is the best way to secure the connection? I am curious for log-ins.
Sending the password in plaintext doesn't seem like a great idea, and hashing it in the client and sending the hash to the server seems equally bad. Is it best to just encrypt the password string, send it over, then decrypt it?
What do you suggest?

I don't know if this helps but you could use JXTA (p2p via java) OR when I was in need of a chat system I used PIRC a java api for making IRC bots, works just as well making a chat system when integrated with a gui. here is the link http://www.jibble.org/pircbot.php

What I am working on is not strictly a chat program, but the same ideas apply. Because of this, I need to log into a server from the client just as an instant messenger would.

Ah, well good luck. I designed a chat program so i can do off-site tech support, it includes everything from file transfers, remote desktop, and soon voice =) all over jxta