Int 6B Fn 19  - Npc Ncsi Extended Serial I/o - Read Data On A Virtual Cir  [S]

   AH = 19h
   AL = virtual circuit number
   CX = number of characters to read
   ES:BX -> buffer for received characters

Return: CX = 0000h if failed
   CX = nonzero (possibly number of characters received) if successful

Note:  this function is also supported by TelAPI

See Also: AX=0100h,AH=12h,AH=18h