Format of APPC/PC "Send_Data" control block:
Offset	Size	Description	)
 00h 12 BYTEs	reserved
 0Ch	WORD	0F00h (verb "Send_Data" or "MC_Send_Data")
 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 #03681)
 16h	DWORD	(big-endian) error code (see #03682)
 1Ah  8 BYTEs	(big-endian) TP_ID
 22h	DWORD	(big-endian) conversation ID
 26h	BYTE	request to send received (0=no, 1=yes)
 27h	BYTE	00h
 28h	WORD	data length
 2Ah	DWORD	pointer to data