INT 68 - APPC/PC - CONNECTION CONTROL - REQUEST TO SEND
        AH = 02h subfn 0E00h
        DS:DX -> control block
Return: control block updated
SeeAlso: AH=02h/SF=0F00h,AH=02h/SF=1000h

Format of control block:
Offset  Size    Description
 00h 12 BYTEs   reserved
 0Ch    WORD    0E00h (verb "Request_to_Send" or "MC_Request_to_Send")
 0Eh    BYTE    1 if MC_ (mapped conversation) form of verb
                0 if basic verb
 0Fh  5 BYTEs   reserved (0)
 14h    WORD    (big-endian) primary return code (see AH=02h/SF=0100h)
 16h    DWORD   (big-endian) error code (see AH=02h/SF=0100h)
 1Ah  8 BYTEs   (big-endian) TP_ID
 22h    DWORD   (big-endian) conversation ID

.