Format of TCPDRV.DOS request block:
Offset	Size	Description	)
 00h	BYTE	(call) function number
		00h initialize ???
		06h get ???
		07h get ???
 01h	BYTE	(call) 00h
		(ret) error code if error, unchanged if successful
 02h	WORD	signature 4354h ('CT')
---function 00h---
 04h	DWORD	(call) pointer to ??? FAR function
		function is called with ES:BX -> device driver request used to
		  invoke this function
 08h  4 BYTEs	???
 0Ch	DWORD	(call) pointer to ??? record, WORD at offset 22h is read
 10h	DWORD	(ret) -> ??? buffer if 0000h:0000h on call
---function 06h---
 04h  4 BYTEs	???
 08h	DWORD	(ret) pointer to ???
---function 07h---
 04h	DWORD	(ret) pointer to ??? record