From the Readme in the docs folder:
MegaMek is a network game. One player hosts a game and the rest of the
players connect. The connecting players can connect from anywhere with a
TCP/IP connection to the host, including the same computer (see hotseat, below.)
You'll probably have to setup port forwarding on your router, and/or add an exception to
your software firewall, like for example the Windows Firewall.
If you have a router:
You need to set up port-forwarding on your router to forward the port that MegaMek uses
(by default 2346) with the TCP protocol to your computer's local IP adress.
For an explanation how to do this on a lot of different routers, visit this website:
http://portforward.com/There, select your router model and then click the "Default Guide" link.
It will guide you on how to do portforwarding on your specific router.
If you have a software firewall, you need to set it up so that it allows incoming
connections to the configured port (by default 2346), with the TCP protocol. On some
software firewalls, you'll also have to set which application should be able to "listen"
on that port. On Windows machines, this is usually "javaw.exe", if you start MegaMek using
the MegaMek.exe file. To be sure, also add that exception for "java.exe".
To host a game, press the "Host a New Game..." button in the main menu. Fill
in your name and click "Okay". The password field allows you to specify a
password for certain server commands. (Type /help in the chat line to get a
list of server commands.) If you don't specify a password, anybody is allowed
to reset the server or kick players, so be careful.
Once the lobby screen comes up, other players can connect and the game can
begin. The other players will need to know the IP address of the host computer.
There are several ways to determine your IP address. On Windows you will need to
open a command prompt and type `ipconfig`. As a last resort, there are some web pages,
such as
www.whatismyip.com that will try to detect your IP address, but if your internet
service uses a proxy or firewall, these pages cannot accurately detect it.
To connect to a game, press the connect button on the main menu and fill in your
player name and the host's IP address.
To play in a hotseat fashion, you can run the host and any number of other
players on the same computer. First, launch and host a game. Then, launch
another copy of the game for each connecting player, and in the "Server Address"
field of the connect dialog, type `localhost`. Each player will need to switch
to his/her copy of the game to play their turn.
