Int 21 Fn FFC3  - Topware Network OS V5.10+ - Get Sharing Status Of Print  [N]

   AX = FFC3h

Return: AL = sharing status of printers (see below)
       FFh if not a printer server

Bitfields for printer sharing status:
 bit 0 LPT1 is shared
 bit 1 LPT2 is shared
 bit 2 LPT3 is shared