Int 21 Fn FFBF  - Topware Network Os V5.10+ - Get Logon User Information   [N]

   AX = FFBFh
   DX:BX -> buffer for logon information (see #2223)

Return: AL = status (00h successful, else failed)
   AH = number of logged-in stations

Format of TopWare logon information:
Offset Size    Description (Table 2223)
 00h   BYTE    station address
 01h 15 BYTEs  username