Custom Races in Assetto Corsa: Server Setup Guide

This guide walks you through creating custom race events on your own Assetto Corsa server. You’ll learn how to set up the server, configure race parameters, and launch a session that you and your friends can join. We’ll cover everything from installing the server files to fine-tuning AI difficulty and weather.

What You’ll Need

• A Windows or Linux machine that can run the server (a dedicated PC or VPS with at least 4 GB RAM is recommended).
• A copy of Assetto Corsa on Steam (you don’t need a separate server license; the server files are free).
• SteamCMD or the official Assetto Corsa server files (available from the Steam store as a free tool).
• Basic text editing skills (you’ll edit .ini and .json files).
• Port forwarding access on your router if you’re hosting from home.

Step-by-Step

1. Download the server files. Use SteamCMD to download the Assetto Corsa dedicated server. In SteamCMD, run: login anonymous, then force_install_dir ./acserver, then app_update 302550. Wait for it to finish.
2. Set up the server folder. After the download, you’ll have a folder called acserver. Inside, you’ll find server and cfg folders. The main configuration file is server_cfg.ini in the cfg folder.
3. Configure the server basics. Open server_cfg.ini in a text editor. Set the SERVER_NAME to something recognizable. Set PASSWORD if you want a private server. Choose a TRACK (e.g., ks_monza) and a CONFIG_TRACK (usually default). Set SUN_ANGLE for time of day (e.g., 45 for afternoon).
4. Set the race mode and laps. In the same file, find the [RACE] section. Set RACE_MODE to 1 for a race (0 is practice, 2 is qualifying, 3 is time attack). Set LAPS to the number of laps you want (e.g., 10). If you prefer a timed race, set TIME to minutes instead (e.g., 30).
5. Add AI opponents. In the [AI] section, set AI_LEVEL from 0 to 100 (higher is faster). Set AI_NUM to the number of AI cars (e.g., 15). You can also set AI_AGGRESSION (0-100) to make them more aggressive.
6. Configure weather and grip. In the [WEATHER] section, set WEATHER_INDEX to a number (0 is clear, 1 is light cloud, 2 is medium cloud, 3 is heavy cloud, 4 is light rain, etc.). Set INITIAL_GRIP (e.g., 98 for slightly slippery) and DYNAMIC_GRIP (e.g., 0 for static).
7. Add your car list. In the cfg folder, create a file called entry_list.ini. Each car entry looks like:

   CAR=ks_ferrari_488_gtb
   SKIN=default
   DRIVERNAME=Player1
   TEAM=MyTeam

   Add as many entries as you want. The car names must match the folder names in your Assetto Corsa content (e.g., ks_mazda_mx5_cup).

8. Set up a race weekend (optional). In server_cfg.ini, you can set PRACTICE, QUALIFY, and RACE sessions with their own durations. For example, set PRACTICE=10 (minutes), QUALIFY=15, and RACE=1 (using laps). This makes a proper weekend format.
9. Start the server. On Windows, run start_server.bat in the server folder. On Linux, run ./acServer from the terminal. The server will read the config and start. Keep the console open; you’ll see logs.
10. Forward ports (if hosting at home). In your router’s settings, forward TCP and UDP ports 9600 and 8081 to your PC’s local IP. 9600 is the game port, 8081 is for HTTP API (optional).
11. Join your server. In Assetto Corsa, go to Online, then Search. Type your server name or IP. If you set a password, enter it. You should connect and be in the session.

Common Mistakes

• Wrong track/car names. The names in the config must exactly match the folder names in the game’s content. If you’re unsure, check the content/tracks or content/cars folders in your Assetto Corsa installation.
• Ports not forwarded. If friends can’t connect, it’s almost always a port forwarding issue. Make sure you’ve forwarded both TCP and UDP on 9600.
• Firewall blocking. Windows Firewall may block the server. Allow the acServer.exe through the firewall.
• Missing entry_list.ini. If the server starts but no cars appear, the entry_list file might be missing or empty. Ensure it’s in the cfg folder and has at least one car entry.
• Using the wrong config file. The server reads server_cfg.ini by default, but if you have multiple configs, make sure the server is using the right one (you can specify with -c flag).

Tips

• Test locally first. Before inviting friends, test the server on your own machine to ensure it works.
• Use a static IP. If hosting at home, set a static IP for your PC to avoid port forwarding breaking after a DHCP change.
• Start with a simple track. Use a default track like Monza or Brands Hatch to avoid missing layout issues.
• Adjust AI level gradually. Start with AI_LEVEL around 80 and tweak based on your skill.
• Backup your config. Copy your working server_cfg.ini and entry_list.ini so you can revert if something breaks.
• Use the HTTP API. You can enable the HTTP API to view live standings via a browser (port 8081).

Troubleshooting

• Server won’t start. Check the console output. Common issues: missing track or car files, incorrect paths, or a corrupt config. Double-check the track name and that the track is installed in the server’s content folder (the server uses its own content, not your game’s).
• Players can’t connect. Verify the server is visible in the LAN tab. If not, check your firewall and port forwarding. Also, ensure the server is not set to LAN_MODE=1 if you want internet players.
• AI cars don’t appear. Check that AI_NUM is greater than 0 and that the entry list has enough cars. AI cars use the same car models as the entry list, so if you have 10 entries and AI_NUM=15, the server will add AI with the same cars.
• Race doesn’t start. If you have a practice/qualifying session, the race will only start after those sessions end. Set them to 0 if you want to go straight to race.
• Server lags. Reduce the number of AI or lower graphics settings on the server (if it’s a dedicated PC, it doesn’t need to render graphics, but CPU load matters). Also, ensure your upload bandwidth is sufficient.

Frequently Asked Questions

Do I need to own Assetto Corsa to run a server?

Yes, you need a Steam account with Assetto Corsa to download the server files via SteamCMD. The server itself is free, but the game is required for the download.

Can I use custom cars and tracks on my server?

Yes, you can add custom content to the server’s content folder. Just copy the car/track folders from your game installation to the server’s content folder, and use the correct names in the config.

How do I make my server visible to the public?

Set LAN_MODE=0 in the config. The server will then appear in the online lobby. You may need to wait a few minutes for it to register.

Can I run a server and play on the same PC?

Yes, but you’ll need a decent PC. The server will use some CPU and RAM, and you’ll also be running the game. It’s recommended to have at least 8 GB RAM and a quad-core CPU.

How do I change the number of laps mid-race?

You can’t change it mid-race. You must edit the config and restart the server.

Why do my friends get a checksum error?

This happens when the server has content that doesn’t match the client’s. Make sure all custom content is identical on both sides, or use only default content.

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