I got the following files off compuserve.  Hope they help.
they worked for me.

                        NULL MODEM HELP

After many of hours trying to make Quake (test1) work with a null modem cable
and reading of other people's problems on Compuserve and on Internet chat
(IRC), I thought I should post the solution which finally worked for me:

Start the computer you've chosen to be the server (the faster of the two),
and type "Quake -listen"  at the dos command prompt (leave quotation marks
out of real commands) while in the Quake directory. Start the other computer
by typing "Quake". Type "yes" on both computers, and then on the server computer
enter "com# -cts -dsr -cd enable". # represents a number 1 or 2 for your serial
port. On the other (client) computer enter the same line, except change the # if
it uses a different com port. On the server computer now enter "map test#",
where # is 1, 2, or 3. It will go into the game and wait. On the client
computer, enter "Connect". NOW you can kill each other!  If this doesn't work,
check your null modem connection with another application. I used Doom2 to
check mine. I haven't been able to get com lines 3 or 4 to work yet, so you may
have to change things around on your computers so that you connect on com 1 or 2.
P.S. I have read other people's accounts that say you must type
"Connect <hostname>" where <hostname> is the name assigned to the server
computer (default="unnamed") on the client computer instead of "Connect",
but I haven't found this to be true for a null modem connection.
If you have problems, you might try it.



                                MODEM PLAY HELP

OK guys here it is modem play in quake....

1) connect via your favorite communications prgm.
	std setting are just fine....
2) exit out without dropping connection
	(decide who will be server and client)
3) server type: quake -listen 2 +map test1 +exec quake1.cfg
	(see below for my CFG file settings)
4) client type: quake +connect +exec quake1.cfg

5) if client dosen't connect on entering the game he should type 
connect on the console until he does (dosen't always go in the 
first time)

that should get you going a 14.4 connect is a little doggy on
the client side (server runs fine ?)28.8 should be fine


CONTENTS OF QUAKE1.CFG:

mouse3 +mlook
mouse1 +attack
mouse2 +strafe
cl_forwardspeed 320
cl_backspeed 320
sensitivity 4
lookspring 1
hostname Mugger's house
color 2 4   <-"shirt / pants color 0-15"
name MUGGER
vid_mode 10
gamma .70
COM1 port 0x3e8 baud 115200 enable
	   ^(im using com3)   ^(won't work without this)

____________________________________________________________
all of these items should be changed to suit you and your system
read the readme and network txt for info on these items...

                         QUAKE CODES

QUAKE CODES v.9

These are the quake codes I've managed to find(not too bad, since I've only
had the game an hour).  Good luck with them, and let me know if you find any
more.

Fly- Flymode
God- Invincibility
Name- Change player name
Notarget- Not sure; may prevent Quake from saying "Target Acquired"
Color (0-13) (0-13)- Change shirt and pant color, where (0-13) is a number
Noclip- No clipping mode
Status- Shows host, map name, no. of players, plus a chart with kills, time in
game, player names
Version- Shows Quake version info
gamma 0.X- changes screen brightness, 0.0-1.0
sv_gravity xxx- 0 for no gravity, about 850 for standard gravity
 
also: hitting 	F10 = Invincibility
	   	 F9 = No clipping mode
		 F8 = Monster tracking off
		  9 = All weapons+ammo

Like I said, this list is probably far from complete.  Let me know if you find
any new codes.

Matt "Dragon" Bell
Compuserve ID 75702,1305