I use the instant chat program ICQ on my laptop. At home when I am dialed in to my Internet provider, I connect fine. But when I take it to work and connect to the network, it will not work even though I have Internet access at work. The purpose is to halt malicious attacks to the network from outside, but some also are set up to limit connections to such programs as ICQ, because you really are connecting to another server when you use that program. You can check with your company's IT department to see if they allow a way to get around the firewall, but I doubt it.
Several companies make such keyboard controllers.
My favorite company for such is Belkin, which also makes dynamite cables. Don't forget you will need some cables to connect the PCs to the switch. The standard switches control up to four PCs with one keyboard, mouse and monitor. My printer, an HP Deskjet 520, just died. I have tried several dealers seeking to have it repaired, and no one will touch it.