Just Cause 3 Multiplayer (JC3:MP) lets you explore the open world of Medici with friends on a dedicated server. This guide covers setting up your JC3:MP server on Legion Hosting, configuring startup variables, editing the config file, and connecting players.
Before You Begin: Make sure you have access to your GPanel account. If you need help locating your server details, see How to Find Your Server IP and Port.
First Start in GPanel
- Log in to GPanel and select your Just Cause 3 Multiplayer server.
- Navigate to the Console tab. The server will download game files via SteamCMD automatically on first boot.
- Wait for installation to complete. You will see progress messages in the console. This may take several minutes.
- Once installation finishes, the server will start automatically. Look for the message
Server successfully started up. - If the server does not start on its own, click the Start button in GPanel.
First Boot Time: The initial SteamCMD installation can take 5-15 minutes depending on network speed. Do not interrupt or restart the server during installation.
Startup Variables
Navigate to the Startup tab in GPanel to view and modify these settings:
| Variable | Description | Default |
|---|---|---|
MAX_PLAYER |
Maximum number of players allowed on the server | 32 |
SERVER_PASSWORD |
Password required to join the server (leave empty for public) | Empty |
SERVER_NAME |
Server name shown in the server browser | Empty |
SERVER_DESCRIPTION |
Server description shown in the browser | Empty |
STEAM_PORT |
Port used for Steam communication | 4202 |
QUERY_PORT |
Steam query port for server browser visibility | Assigned automatically |
HTTP_PORT |
HTTP port for the server's web interface | Assigned automatically |
AUTO_UPDATE |
Automatically update the server on startup (1 = on, 0 = off) | 1 |
Server Configuration
The main configuration file is config.json in the server's root directory. You can edit it via the File Manager in GPanel or via SFTP.
Example config.json
{
"announce": true,
"description": "My JC3 Multiplayer Server",
"host": "0.0.0.0",
"httpPort": 4201,
"logLevel": 7,
"logo": "",
"maxPlayers": 32,
"maxTickRate": 60,
"name": "My JC3:MP Server",
"password": "",
"port": 4200,
"queryPort": 4203,
"requiredDLC": [],
"steamPort": 4202
}
Port Values: The
port, queryPort, httpPort, and steamPort values in config.json are automatically set by GPanel from your startup variables. Do not change them manually unless you know what you are doing.
| Setting | Description |
|---|---|
announce |
Whether the server appears in the public server list (true/false) |
logLevel |
Logging verbosity (0-7, where 7 is most verbose) |
maxTickRate |
Maximum server tick rate (FPS). Default is 60. |
requiredDLC |
Array of DLC IDs required to join the server |
Restart Required: After editing
config.json, restart your server from GPanel for changes to take effect.
How to Connect
- Install the Just Cause 3: Multiplayer Mod from the Steam Store (it is a free standalone application).
- Launch Just Cause 3: Multiplayer Mod from your Steam library.
- In the server browser, search for your server by name.
- Select your server and click Connect.
- If the server is password-protected, enter the password when prompted.
Via Direct IP
- In the JC3:MP launcher, look for a Direct Connect option.
- Enter your server IP and port in the format
IP:PORT. - Click Connect.
Finding Your IP: Your server IP and port are displayed on the main page of your server in GPanel. Ports are randomly assigned unless you have a private IP. For detailed instructions, see How to Find Your Server IP and Port.
Scripting and Modules
JC3:MP supports server-side scripting with JavaScript. Scripts and modules are placed in the server's packages/ directory. Each package has its own folder with a main.js entry point.
For scripting documentation, see the JC3:MP Wiki.
Related Articles
- Just Cause 3 Multiplayer Admin and Commands
- How to Find Your Server IP and Port
- How to Upload Files via SFTP
Need Help? If you encounter any issues not covered in this guide, open a support ticket and our team will assist you.
