Int 21 Fn FFC4  - Topware Network Os V5.10+ - Get/set Lpt Port On Print S  [N]

   AX = FFC4h
   BL = subfunction
       00h get

       Return: AL = mapped printer port on print server
       01h set
       CL = network printer port (00h LPT1, 01h LPT2, 02h LPT3)
   CH = local printer (00h LPT1, 01h LPT2, 02h LPT3)