# SteamCMD servers

Use `modules.services.steamcmd` as the low-level runner for one SteamCMD server.
Create a game module under `configs/nixos/modules/services/games/` for each game.

The game module owns game-specific defaults and command-line flags.
The host owns deployment-specific paths, names, secrets, and network placement.

## Create a game module

1. Create `configs/nixos/modules/services/games/<game>.nix`.
2. Define options under `modules.services.games.<game>`.
3. Expose only values the host must choose.
4. Map those values to `modules.services.steamcmd`.
5. Set the Steam dedicated-server app ID in the game module.
6. Set the server executable in the game module.
7. Generate game-specific arguments in the game module.
8. Open the game's documented UDP ports in the game module.

Keep `modules.services.steamcmd` focused on shared SteamCMD behavior.
Do not put game-specific flags or port rules there.

## Configure a host

During validation, enable the game module directly on a host.

```nix
modules.services.games.valheim = {
  enable = true;
  steamDir = "/pikachu/data/steamcmd";
  installDir = "/pikachu/data/servers/valheim/main";
  stateDir = "/pikachu/media/games/servers/valheim/main";
  serverName = "main";
  password = "foobarbaz";
};
```

Use host paths for direct host deployment.
Use guest paths after the server moves into a guest.

## Deploy and test

1. Evaluate the host configuration.

   ```sh
   nix eval .#nixosConfigurations.<host>.config.system.build.toplevel.drvPath --raw
   ```

2. Deploy the host.

   ```sh
   deploy-to <host>
   ```

3. Check the game service.

   ```sh
   sudo systemctl status <game>.service
   sudo journalctl -u <game>.service -n 200 --no-pager
   ```

4. Check UDP listeners.

   ```sh
   sudo ss -lunp | grep -E '<port>|<port-plus-one>|<game>'
   ```

5. Connect from the game client.

The Valheim server is ready after the log contains `Game server connected`.
It can spend time generating a new world before it accepts connections.