Windows license servers require that a special hardware key called a SentinelPro Hardware Key be installed with your license manager. You will receive this key and a corresponding license file from ESRI Customer Service. The hardware key plugs into the parallel port on back of the license manager server.
The license file you install with your license manager contains keycodes that are used to control software access. These keycodes are based upon a unique identifier. Your hardware key provides the unique ID number used in your license file. The license manager compares the keycodes in the license file and the unique identifier for a computer to allow access to the software. If the keycode and the unique identifier agree, then software access is granted.
No hardware key is needed with a UNIX license manager because the computer host ID is used for the unique identifier.