Format of Excelan request packet:
Offset	Size	Description	)
 00h 12 BYTEs	???
 0Ch	WORD	(ret) error code (see #03273)
 0Eh	DWORD	-> FAR function for ???
 12h	WORD	function number
		0001h ???
		0002h NOP
		0003h NOP
		0004h NOP
		0005h ???
		0006h get ??? record
		0007h NOP
		0008h reset ???
		0009h NOP
		000Ah set ???
	???
---function 01h---
 20h	BYTE	(call) subfunction (32h-3Bh)
		3Bh non-blocking I/O request (will be tested every clock tick)
 21h	BYTE	(ret) error code
		00h successful
		09h invalid connection number
		2Ah bad connection type
		45h ???
---function 01h, subfunction 32h---
 3Ah	WORD	(call) connection type (01h stream, 02h datagram)
---function 01h, subfunction 34h---
 26h	WORD	(call) ???
 28h	WORD	(call) ???
 2Ah	WORD	(call) ???
---function 01h, subfunction 35h---
 1Ah	WORD	(call) connection number???
 26h	WORD	(ret) ???
---function 01h, subfunction 36h---
 1Ah	WORD	(call) connection number???
 38h	WORD	???
---function 01h, subfunction 37h---
 24h	WORD	(ret) ???
 26h	WORD	(ret) ???
---function 01h, subfunction 38h---
 1Ah	WORD	(call) connection number???
---function 01h, subfunction 3Ah---
 22h	WORD	(call) ???
		667Eh ???
		667Fh ???
 24h	BYTE	(call 667Eh) ???
 24h	WORD	(return 667Fh) ???
---function 01h, subfunction 3Bh---
 0Eh	DWORD	(call) -> function to invoke for I/O or 0000h:0000h
		function called with AX = 0000h
				     STACK: DWORD -> request packet
					    WORD 0000h
			should return STACK unchanged
 1Ah	WORD	(call) connection number???
 21h	BYTE	(ret) set to 01h when I/O becomes possible
 22h	BYTE	(call) direction (00h write, 01h read)
 34h	DWORD	(ret) -> next pending request packet
---function 05h---
 1Eh	WORD	(call) ???
 20h	WORD	(call) ???
 34h	DWORD	(call) -> ???
---function 06h---
 16h	DWORD	(call) -> buffer for ??? record (see #03274)
 1Ah	WORD	(call) number of bytes to copy
 22h	WORD	(ret) number of bytes transferred
---function 08h---
 14h	WORD	(ret) ??? (0001h)
---function 0Ah---
 16h	DWORD	(call) -> WORD ???
 1Ch	WORD	(call) must be 000Ah for BWLWP35