Just to clarify a single important point: yes this code can handle multiple simultaneous client connections, but there is one limitation: the server can only deal with one client at any one moment in time. So if the server takes a lot of processing time to handle client input, then all other clients will have to wait in line for their turn to communicate with the server.

This is not a big deal with most servers that communicate back and forth one a one-line-at-a-time basis, but as soon as you throw in extreme processing or any sleep()s, etc, things can back up quickly.