Format of APPC/PC control block:
Offset	Size	Description	)
 00h 12 BYTEs	reserved
 0Ch	WORD	verb (action)
		2500h TP_ENDED
		2900h TP_VALID
 0Eh  6 BYTEs	00h
 14h	DWORD	(big-endian) return code (see #03668)
 18h	WORD	00h
 1Ah  8 BYTEs	(big-endian) TP_ID
 22h	DWORD	-> CREATE_TP record (only if verb = 2900h)