When faced with such problems, I always turn to netcat, a small, powerful utility for creating/testing/troubleshooting TCP and UDP connections.
It is available Windows, but since it is operated from the command-line, not many Windows users knows about it, so the guides you will find will probably be geared towards Unix/Linux users:
http://www.linuxforums.org/network/having_fun … th_netcat..html
Start by downloading and installing netcat. OBS: Beware that your anti-virus program may well flag it as malware / hacking tool and take steps to block/delete it!!
Then test it locally:
Start 2 CMD windows on PC #1.
In CMD #1 start netcat so it listens on TCP port 5000:
netcat -l -p 5000
In CMD #2 start netcat and make it connect to port 5000 locally:
netcat 127.0.0.1 5000
Now start typing! Press CTRL-C to stop.
Now that you know how to make netcat listen on TCP 5000, start it again, and start CMD + netcat on PC #2, and have it connect to port 5000 on PC #1:
netcat nnn.nnn.nnn.nnn 5000
nnn.nnn.nnn.nnn is of course the IP address of the other PC, or the external IP address of the router that PC #1 uses to connect to the Internet. Easiest way to find that is to go to http://whatismyipaddress.com/.
If all this remote netcat'ing works, then you know that you got your router and IP-addresses set up correctly. After that you can start figuring out why the multi-player game does not work in DOSBox.
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