

	ComRing - packet driver for "network" based on serial ports
			      version 1.17
		    Copyright 1997,8 by Jan Bobrowski
	     This is free software. Use it at your own risk.
			 Distribution unlimited.


 MOTIVATION

	The intention of ComRing is to connect more than two computers
	through	ordinary serial ports. ComRing cable allows you to
	build "network" based on serial ports using one port per
	computer. It is slow but cheap.

	ComRing software also offers network interface for traditional
	Null-modem. It may be useful for games that don't handle it
	properly.

 HARDWARE

	Serial port was developed for computer-modem connection. It is
	widely used to connect two computers using null-modem cable.
	It consists of two units: trasmitter and receiver. They may be
	connected to different computers (?). The basic idea of ComRing
	is to organize computers in logical form of ring. Data will flow
	in fixed direction.
				A -----> B
				^	 |
				|	 |
				|	 v
				D <----- C

	You should prepare 3-wire ComRing cable:

	line  DB9 DB25
	 TxD   3   2	transmit   connected to RxD of next computer
	 RxD   2   3	receive	   connected to TxD of previous computer
	 GND   5   7	ground	   common for all computers

	  DB25					 DB9
	   _____________________________	  _____________
	 1 \ . T R . . . G . . . . . . / 13	1 \ . R T . G / 5
	 14 \ . . . . . . . . . . . . / 25	 6 \ . . . . / 9
	      -----------------------		     -------

	Cable for three computers:

		Computer A	Computer B	Computer C

		   TxD ----------- RxD
				   TxD ----------- RxD
		   RxD --------------------------- TxD
		   GND ----------- GND ----------- GND

	Cable for four computers:

	Computer A	Computer B	Computer D	Computer C

	   TxD ----------- RxD
			   TxD --------------------------- RxD
					   RxD ----------- TxD
	   RxD --------------------------- TxD
	   GND ----------- GND ----------- GND ----------- GND

	You can use Null-modem cable as two-node ComRing.

 SOFTWARE

	ComRing cable for more than two computers will not work with an
	ordinary SLIP or PPP packet driver. You can't use it as null-modem.
	I wrote special packet driver (comring.com) to make it usable. 
	It is class 1 driver - it emulates DIX ethernet (specification 1.11, 
	basic and high-performance functions). You must install it on each
	computer to close circuit.

	To distinguish between different computers in the "network" specify
	a single letter, identifying your computer. It is the first parameter
	(and only required) to the packet driver. When you invoke `comring a' 
	on one computer you can't use `a' (or `A') on others. This letter is 
	used to generate ethernet address.

	Syntax is:	comring id [parameter]...

	You may use following parameters:

	   com#	    com port (default: 2)
	   baud=#   baud rate (default: 115200, it may be slowed down)
	   nodes=#  maximal number of computers connected (default: 3)
	   int=#    interrupt for packet driver (hex, default: 60)

	If you're using nonstandard port you should specify:

	   port=#   port address
	   irq=#    irq number

	Example:  comring A baud=9600 com1

	Note: Comring is supposed to be a DOS program. It can interfere
	with Windows, however probably it will work in DOS box.

 GAMES

	Most games don't use packet driver interface. They expect IPX
	network. You may use Intel's `pdipx' adapter included in this
	package. It has been configured for DIX ethernet (command:
	econfig.exe pdipx.com shell:e 8137).

	Invoking commands may look like:

		comring B com1 baud=57600
		pdipx
		game

	You should remember: if one computer will not work correctly,
	the whole network won't work.

	Please send me success/failure reports. (jb@wizard.ae.krakow.pl)
