how to find what other computers connected to you on local network?

Way back when if i remember correctly, there was a control panel or utility in the OS that showed you what other users in your local network were connected to your work station so if need be you could disconnect them or warn them when you had to shut down.

But now, if I go to restart or shut down, you get the warning that other users are connected but there doesn't seem to be a way to determine who.

What am I missing? Anyone know a quick way with the software available that comes with your Mac OS, or is there a Free Utility I can download?

This is a business work station that is networked with other Macs and Windows computers of different system versions. My station is running Mac OS 10.8.5.

Thanks.