Me and a friend want to play co-op Shattered Steel since he has a dated PC and can't play MW4 Merc on his rig (MW4 merc is free by the way) and I can't make head or tails of the multiplayer options, so does anyone know how to use co-op mode on this game?

i don't know if the dosbox is already configured for it, but i was looking in the read-me file of the dosbox archive and it was saying that u can run serial through network...

8. Serial Multiplayer feature:
==============================

DOSBox can emulate a serial nullmodem cable over network and internet.
It can be configured through the [serialports] section in the DOSBox
configuration file.

To create a nullmodem connection, one side needs to act as the server and
one as the client.

The server needs to be set up in the DOSBox configuration file like this:
serial1=nullmodem

The client:
serial1=nullmodem server:<IP or name of the server>

Now start your game and choose nullmodem / serial cable / already connected
as multiplayer method on COM1. Set the same baudrate on both computers.

Furthermore, additional parameters can be specified to control the behavior
of the nullmodem connection. These are all parameters:

* port: - TCP port number. Default: 23
* rxdelay: - how long (milliseconds) to delay received data if the
interface is not ready. Increase this value if you encounter
overrun errors in the DOSBox Status Window. Default: 100
* txdelay: - how long to gather data before sending a packet. Default: 12
(reduces Network overhead)
* server: - This nullmodem will be a client connecting to the specified
server. (No server argument: be a server.)
* transparent:1 - Only send the serial data, no RTS/DTR handshake. Use this
when connecting to anything other than a nullmodem.
* telnet:1 - Interpret Telnet data from the remote site. Automatically
sets transparent.
* usedtr:1 - The connection will not be established until DTR is switched
on by the DOS program. Useful for modem terminals.
Automatically sets transparent.
* inhsocket:1 - Use a socket passed to DOSBox by command line. Automatically
sets transparent. (Socket Inheritance: It is used for
playing old DOS door games on new BBS software.)

Example: Be a server listening on TCP port 5000.
serial1=nullmodem server:<IP or name of the server> port:5000 rxdelay:1000

So i got it working, and just played it with my brother.

You really have to change the serial configuration on the dosbox to get it working.

So, in wherever you installed the game, on it's folder there is a file named "dosbox.conf" , you will have to configure it for the computers who are going to play together.

Choose a computer to be the Hoster/Server, in the server you must open the file with a notepad and nearly at the end of the file there is a part to configure the dosbox serial.

On the Hoster/Server:
There is 4 ports, which means Serial 1 = COM1, Serial 2 = COM2 and on... put

serial1=nullmodem port:5000

On the Client:

I use static ip configuration, so if you use dynamic your server ip will always change and you will have to configure it every time you are gong to play. To see your hoster ip open the command console and run the command ipconfig (IPv4 Address) on the hoster computer.

serial1=nullmodem server: 192.168.254.4 port:5000

The server ip here is the ip that I'm using on my computer, so your might be different.

Just got this now, Thanks!