Int 21 Fn 5F81  - LANtastic - Login To Server                              [N]

   AX = 5F81h
   ES:DI -> ASCIZ login path followed immediately by ASCIZ password
   BL = adapter number
       FFh try all valid adapters
       00h-07h try only specified adapter

Return: CF clear if successful
   CF set on error
       AX = error code

Notes: login path is of form "\\machine\username"
   if no password is used, the string at ES:DI must be terminated with
     three NULs for compatibility with LANtastic v3.0.

See Also: AX=5F82h,AX=5F84h