Asynchronous multichat server

in our CN pracs sir is asking us to make an Asynchronous multichat server.what does he mean by this? (how is it different?).
what are the things to be used ?(i heard something like signal handling etc...)
please give a link of tutorial or something on the net that can help others.

it means that server can handle multiple clients through OS.
As soon as client connects server transfer the connection to OS and wait for the other client.Now the transmission and reception is to be handled by OS.This is done by fork() system call whereas in asynchronous multichat program handles each client sequentially one by one.
Only this much i know, searching for a gud tutorial still.