If you want to see who is currently using the ZEMAX licenses supported by your network key then start Internet Explorer on the client,  and type the following into the address bar:

http://{IP address of keyserver}:7002

For example, if the keyserver is on 10.0.0.1 you would enter:

This shows that currently 4 of my 10 licenses are in use. Who is using them? Just double-click on the key# of the key whose details you want to see. For the above screenshot, I double-clicked on "1" and got:

double-clicking on the key# again shows:

This shows the name of the machine that is using each license, the currently logged-in user on that machine, and when the license was first obtained. When a client machine closes ZEMAX it will disappear from this list. Only machines currently running ZEMAX account for a license.