FreeOrion supports multiplayer games in a host-client mode. One player's computer acts as the game server, which the other players' computers must connect to. Multiplayer in hotseat mode is not supported directly, but could be emulated by running several clients on the same computer, and trusting opponents not to look at each others' clients.
Hosting a game
To host a multiplayer game, choose "Multiplayer" and enter your player name. Player names should contain only letters, numbers and underscores (a-z, A-Z, 0-9, _) and no spaces.
After pressing "Okay", you will see a window "Multiplayer Setup", where you can configure the game parameters.
Please note that player names, empire names and colours must be choosen unique, or the button "Start Game" will not be active.
Joining a game
In the main menu choose "Multiplayer", enter your player name and choose a game out of the list. Or you can manually enter a host name or IP address at the bottom of this page.
FreeOrion multiplayer connections use TCP port 12346. You may need to forward this port in your router or firewall.
The discovery port uses UDP 12345 and is used to detect available game hosts. You don't need to forward this port to run a game.