I'm very experienced in client/server/Winsock programming, and personally, I hate RFCs. They make things more confusing than they need to be for, I guess, the sake of conforming to "standards".

You should look at either the data received within the DataArrival event (this is VB6/Winsock right? Or something else?), and use some common sense/logic on how to figure out who the users are and how many.

There are also a lot of IRC examples at:
http://www.pscode.com

I've only briefly messed with the IRC protocol so I can't say from memory.

You can also google for "IRC Protocol Specification -RFC" and you might find an article by someone that is easy to follow and understand.