If you want to host multiplayer network games, you need to set up the OpenTTD server on your computer.
1 From the Main Menu, click Multiplayer
2 Click Start Server
3 Pick a name for your game to help others identify it, and enter it into the Game name box
4 Configure the additional settings, explained below:
5 Click New Game (to generate random new game), or Load Game (to continue an saved game), or Play Scenario, or Play Heightmap, or Cancel.
- Set Password sets a password for the server so that only users who know the password can join your game.
- Connection specifies whether the server is for LAN use only, or if it advertises itself to the master server so that it shows up in the internet server list.
- Language Spoken is for requesting that users speak a certain language on your server.
- Max clients limits the total number of clients (players and spectators) that can connect.
- Max companies limits the number of companies at game.
- Max spectators limits the number of clients who can connect to watch but not play (not-players).
If your computer is behind a firewall or NAT router, you should check that the correct ports (port 3979 by default) are open or forwarded. You can change the port used by entering "server_port <port>" into the game's console.
If you are expecting many players and aren't going to be using the machine yourself to play, you can start OpenTTD as a dedicated server instead of the usual interactive graphical version.