Format of NetWare TCP/IP Request Control Block (RCB):
Offset	Size	Description	)
 00h	DWORD	-> next RCB
 04h	DWORD	-> previous RCB
 08h	DWORD	-> FAR post routine called if bit 7 of function code set
 0Ch	BYTE	flags (internal use)
		bit 0: request in progress
		bit 1: posted
		bit 2: Windows
		bit 3: "PROTBUF"
		bit 4: "ABORTRCB" for Ctrl-Break handling
		bit 5: call INT 21/AX=0B00h while blocking
 0Dh  7 BYTEs	???
 14h	BYTE	(ret) temporary result code
 15h	BYTE	(call) function code (bit 7 set if non-blocking) (see #02902)
 16h	BYTE	socket number
 17h	BYTE	(ret) result or error code (see #02905)
---accept/bind/connect/getmyipaddr/getpeername/getsockname commands---
 18h		sockaddr structure (WORD port + DWORD IP address)
---close comand---
 no additional fields
---getmymacaddr command---
 18h  6 BYTEs	low-level hardware network address
---BOOTP command---
 18h 64 BYTEs	BOOTP VSA data (see #02906)
---getpathinfo command
 18h  8 BYTEs	key
		"TCP_CFG" used by PING.EXE
 20h 128 BYTEs	path
 A0h	WORD	length of path in previous field
---getsockopt/setsockopt commands---
 18h	WORD	option name
		0004h SO_REUSEADDR
		0008h SO_KEEPALIVE
		0080h SO_LINGER
 1Ah	WORD	option value
 1Ch	WORD	"linger"
---getsubnetmask command---
 18h	DWORD	sockaddr structure (WORD port + DWORD subnet mask)
---ioctl command---
 18h	DWORD	argument value
 1Ch	WORD	ioctl number
---listen command---
 18h	WORD	maximum allowable connection backlog
---select command---
 18h	WORD	number of sockets
 1Ah		fd_set readfds (bitmap of sockets)
		fd_set writefds
		fd_set expectionfds
	DWORD	timeout in clock ticks
---shutdown command---
 18h	WORD	shutdown type
---socket command---
 18h	WORD	protocol (1 = ICMP, 6 = TCP, 17 = UDP)
---I/O commands (recv,recvfrom,send,sendto)---
 18h	WORD	flags
 1Ah  6 BYTEs	sockaddr from/to
		WORD	port number
		DWORD	IP address
 20h	WORD	length of packet sent/received
 22h	WORD	number of pointer/length pairs following (max 8)
 24h 6N BYTEs	buffer descriptors, each
		Offset	Size	Description
		 00h	DWORD	pointer to buffer
		 04h	WORD	length of buffer
---getsnmpinfo command---
 18h	DWORD	(ret) -> ??? data in TCPIP code segment
--getifn command---
 18h	WORD	interface number
 1Ah	WORD	MLID instance number
 1Ch 128 BYTEs	MLID name
---getipinfo/setipinfo commands---
 18h	WORD	interface number (00h = default)
 1Ah	DWORD	IP address
 1Eh	DWORD	IP netmask
 22h  3 DWORDs	router addresses (00000000h = unused entry)
---getdnsinfo/setdnsinfo commands---
 18h	WORD	interface number (00h = default)
 1Ah  3 DWORDs	name server IP addresses (00000000h = unused entry)
 26h 128 BYTEs	domain name
---getroutes/setroutes/removeroutes commands---
 18h	WORD	number of route entries to follow (max 5)
 1Ah 10N BYTEs	route entries
		DWORD	destination host/net IP address
		DWORD	IP address of first router
		WORD	route type
---getarpe/setarpe/removearpe commands---
 18h	WORD	number of ARP entries to follow (max 16)
 1Ah 10N BYTEs	ARP entries
		DWORD	destination IP address
		6 BYTEs	destination hardware address
---other commands---
 18h  4 WORDs	parameter words 0 to 3 (see #02902 for usage)