How to Join Your Kerbal Space Program Server

Kerbal Space Program has no built-in multiplayer mode. Your server uses the community modification DarkMultiPlayer (DMP) for that. Every player needs the matching DMP client in their KSP installation – without the mod there is no way to join a server from inside the game.

Find connection details

Important

You need the IP address and the Game Port of your server. You can find both in the dashboard of your server. DarkMultiPlayer does not use a Query Port – the server only uses a single port.

Install the DMP client

1. Download the client
   Open d-mp.org/downloads and download the file DMPClient.zip.

2. Open the KSP folder
   Open the installation folder of Kerbal Space Program. On Steam you get there by right-clicking the game in your library and choosing Manage → Browse local files.

3. Extract the mod
   Extract the archive and copy the folder DarkMultiPlayer from DMPClient/GameData/ into the GameData folder of your KSP installation. The resulting path looks like this:

   [KSP folder]/GameData/DarkMultiPlayer/

4. Start the game
   Launch Kerbal Space Program. The DarkMultiPlayer window with the installed version now appears in the main menu.

Warning

Client and server have to use the same DMP version. If they do not match, the server rejects the connection with the message Protocol mismatch. Always download the client from d-mp.org again after your server has been updated.

Note

The current DMP version is built for KSP 1.12.x only. On any other game version the mod disables itself – instead of the DMP window, the main menu then shows a compatibility warning from Kerbal Space Program.

Add the server and join

1. Set your player name
   Enter your name in the Player name field of the DMP window. It can be up to 32 characters long.

   Note

   The characters < > : " / \ | ? * $ are not allowed in a player name. The names Initial, Shared and the console name of the server (Server by default) are reserved as well.

2. Add the server
   Click on Add. Three input fields appear:

   Field	Value
   Name	Any display name you like for your server
   Address	The IP address of your server from the dashboard
   Port	The Game Port of your server from the dashboard

   Warning

   The fields come pre-filled with default values (127.0.0.1 and a default port). Replace both values with the details from your dashboard.

3. Save the entry
   Click on Add server. Your server then shows up in the server list of the client.

4. Connect
   Select the entry in the list and click on Connect. The entry is saved – next time you only have to select it and click Connect.

Server does not show up in the public list

The Servers button in the DMP client shows a public server list. That list comes from central master servers a server has to report to actively. Your server is not listed there by default.

Note

Add your server manually with its IP address and Game Port as described above. This is the intended way and works regardless of the public list.

Player name and keys

The first time you join, the server creates a file containing your public key:

/Universe/Players/<player name>.txt

From that moment on the player name is tied to your key pair and nobody else can use it. Your keys are stored locally at:

[KSP folder]/GameData/DarkMultiPlayer/Plugins/Data/publickey.txt
[KSP folder]/GameData/DarkMultiPlayer/Plugins/Data/privatekey.txt

Tip

If you switch to a different PC or reinstall KSP, copy both key files along – otherwise you can no longer use your existing player name. The mod also stores a backup in saves/DarkMultiPlayer/. If the keys are lost, an admin can delete the file /Universe/Players/<player name>.txt on the server – the name is free again afterwards.

Connection is rejected

Message	Cause
Protocol mismatch	Client and server use different DMP versions
Invalid username	The player name is empty or contains forbidden characters
Kicked for using a reserved name	The name is reserved (Initial, Shared or the console name of the server)
Client already connected	A player with that name is already connected
Public/private key mismatch or Invalid key for user	The player name belongs to a different key pair on this server
You were banned from the server!	You are banned, see Kick & Ban Players
Server is full	The maximum number of players has been reached

Which ports does DarkMultiPlayer use?

A DMP server uses exactly one port: the Game Port over TCP. Connection handling and all game data run through it. There is no separate Query Port. You can see the Game Port that applies to your server in the dashboard.

Tip

If your server uses mods, all players need the same mods locally in their GameData folder. How that is set up is described in Add Mods.