ipx_IPX

Using The IPX Network Protocol

==============================

This document describes the purpose of the files RIPX.H, RIPX.C and

CHAT.C and how they use IPX to transmit packets over a local area

network. Firstly, many thanks must go to Daniel Parnell

(daniel@bunyip.ph.rmit.oz.au) for his general info on IPX programming

and background (See Below).

To use IPX you must obviously have a network card and the necessary

drivers. The IPX driver PDIPX.COM interfaces with your network card via

All routines should be re-compiled using the LARGE memory model. If you

are looking to use protected mode then you should try and find a file

called IPXPMODE.ZIP. I haven't included my protected mode version 'cos I

use the underestimated Symantec C/C++ compiler which comes with its own

DOS extender. This differs quite markedly from the 'normal' Watcom

compiler. IPXPMODE.ZIP is based on using Watcom though.

If you find these routines useful, drop me a line.

CyberFrog 8:) (RoccoLoscalzo@compuserve.com)

*************************************************************************

IIIIII PPPPPP XX XX

II PP XX XX

II PP XX XX How to send IPX packets over

a

II PP XX XX network by Daniel Parnell

IIIIII PP XX XX s921878@minyos.xx.rmit.oz.au

daniel@bunyip.ph.rmit.oz.au

Started : 29th March 1994

Last Mod: 2nd September 1994

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

=-=

were before closed to me. NETWORKED GAMES!!! :) This document

Admittedly, it has only been 5 days since my first sucessful packet, but

that short time I have developed a set of routines that seem to work quite

well. :) These routines are included in appendix A and an example

program

is included in appendix B. These routines are written in Turbo Pascal

6.0,

but should be reasonably portable to other languages.

packets

one

all

machines is called a BROADCAST. A broadcast will usually be confined to

just

the local network, however there are ways around this which I will not go

into here. ;) These packets have a specific structure which is shown in

figure 1.

Figure 1 - The IPX header

-----------------------------------------------------------------------

-

| Name | Size (bytes) | Description

|

----------------|--------------|---------------------------------------

|pType | 1 byte | Packet type (always use 0)

|

|src | 12 bytes | Address of source node

|

----------------|--------------|---------------------------------------

|

By the way, bigendian means that the first byte holds the most

significant

value, which is the opposite of the normal way of doing things on the PC.

For reasons better known to Novell, the checksum is always set to $ffff.

has been through. The format of the address is shown in Figure 2.

-----------------------------------------------------------------------

| Name | Size (bytes) | Description

|

----------------|--------------|---------------------------------------

|

|network | 4 bytes | Network address

Sockets are a device that lets a node decide if it will act on a packet.

It allows multiple programs on the one PC to use IPX packets completely

transparent to the others. It also means that a broadcasted packet will

be received by a machine if it has a socket open for that which the packet

addressed. So packets can be ignored by nodes that are not capable of

accepting them. Special care must be taken to ensure that no two programs

try

to send different types of packets to the same socket!

The next order of bussiness is to tell the PC that we want to open a

-

| Name | Size (bytes) | Description

|

----------------|--------------|---------------------------------------

|

|Link | 4 bytes | Pointer to next ECB?

|

|ESR | 4 bytes | Pointer to Event Service Routine

|

|InUse | 1 byte | Flag telling the ECB status

|

|complete | 1 byte | Flag telling the ECB completion code

|

|socket | 2 bytes | Bigendian socket number for ECB

|

|IPXwork | 4 bytes | Work space for IPX

|

|Dwork | 12 bytes | Work space for driver

|

|fragCount | 2 bytes | Number of fragments

|

|FragData | 4 bytes | Pointer to data fragment

|

|FragSize | 2 bytes | Size of data fragment

|

----------------|--------------|---------------------------------------

a packet has arrived. I don't see this as any great drawback however.

To send a broadcast, set the node address to all $ff. This is done

automatically by my routines.

FragData must be initialized to point to the IPX header and the data we

seen in Appendix B in the definition of the record type "Packet". The ECB

do

so.

Interrupt $7A is assigned to the Novell API, and is the old way of

method

(in my opinion anyway). The sub-functions that we use are given in Table

1.

--------------------------------------------------------------------------

---

|Function|Name |Regs

|

--------------------------------------------------------------------------

---

| | |Returns:AL=Error code DX=Socket Number

---

| $0001 |Close Socket|DX=Socket number (bigendian)

|

--------------------------------------------------------------------------

---

| $0003 |Send Packet |ES=Seg of ECB SI=Offset of ECB

|

--------------------------------------------------------------------------

|

|

---

| $0009 |Get Local |ES=Seg of address array SI=Offset of address

array |

| |Address |

--------------------------------------------------------------------------

| $000A |Im Idle |None

---

NOTE: The function number is stored in BX.

See the procedure InitIPX in appendix A for an example of this.

tell the IPX driver about them. First we will look at a recieving ECB

and

IPX header, followed by a sending.

For a recieve record, the IPX header does not need to be initialized at

all.

However, I think it is a good idea to zero all the fields just be on the

safe

side. The ECB however, does need to have several fields set. The inUse

flag

should be set to $1D (don't ask me why, actually it works without this,

but

several of the recources I consulted did this). The socket number must be