ServerStarterJar

ServerStarterJar is a same-process wrapper around the Forge (1.17+) and NeoForge server run scripts.

This project brings back the server.jar file in old versions, that can be used when a server host does not support custom launch scripts (such as the run.sh file).

Installation

To use the starter, simply download the server.jar file of the latest release and place it in the folder the run.sh/run.bat scripts are located (you may need to run the NeoForge installer first with the --install-server argument; check the installer section for more information).
Afterwards, you may run the jar as an executable (i.e. java -jar server.jar).

[!IMPORTANT]
Any JVM arguments (such as -Xmx) placed in the user_jvm_args.txt file will not be picked up by default. You'll need to run java @user_jvm_args.txt -jar server.jar.

Compatible Versions

This starter is compatible with all MinecraftForge versions since 1.17, and with all NeoForge versions.

Running the installer

If the starter cannot find the run scripts, it will attempt to run an installer.
It will first try to run the first file ending with -installer.jar from the folder.

You may specify an installer to download instead using the --installer option (i.e. java -jar server.jar --installer 21.0.46-beta).
The installer specified can either be a link to an installer (i.e. https://maven.neoforged.net/releases/net/neoforged/neoforge/21.0.46-beta/neoforge-21.0.46-beta-installer.jar) or a NeoForge version to download the installer for (i.e. 21.0.46-beta).

[!NOTE] The installer will only be run if the starter cannot find the run scripts. You may force it to run if the installer version and the installed version differ using --installer-force.

How it works

Below you will find the steps the start goes through to launch a modular NeoForge environment:

1. search the folder the starter was invoked in for the run.sh (*nix) / run.bat (Windows) file
2. find the java invocation in the run script
3. extract and parse any argument file references (@[...])
4. if a -jar argument is found:
   • put it on the system classpath alongside all entries specified in the Class-Path manifest entry
   • update the java.class.path system property with the new entries
5. otherwise
   • parse the module path (-p) argument, and load the jars on a new module layer, which will replace the boot layer
   • parse the --add-exports/--add-opens arguments and replicate them using Java instrumentation module redefinition
   • ignore the --add-modules arguments as they're irrelevant since the module path is fully loaded as the boot layer
6. set the system properties (-D<name>=<value>) specified by the args file
7. consider the Main-Class attribute of the jar / the first remaining argument the main class, load it, and retrieve its main(String[]) method
8. append any arguments specified to the starter executable to the remaining arguments 9
9. launch Minecraft with the remaining arguments