server.jar

This feature is exclusive to Java Edition.

 

server.jar

Author(s)	Mojang Studios
Platform(s)	and other platforms that support running a JVM
Written in	Java
Latest version	Release: 1.21.8
Release date	June 8, 2009
Size	Only JAR: ≈ 54 MiB With initial generated data: ≈ 114 MiB
License	EULA
Source available	Partial
Links	Website

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There is a related tutorial page for this topic!

 

See Tutorial:Setting up a Java Edition server.

server.jar is an executable JAR file providing the server software used to host a Java Edition server. It is distributed by Mojang Studios and can be downloaded for free.

Code is shared between the server.jar and the client.jar, meaning they are identical in gameplay. The client.jar provides an internal server used for playing singleplayer worlds, but server.jar does not provide a client.

Contents

The server.jar contains the program and resources necessary to run a Minecraft server. When ran using JVM, these resources are extracted into the working directory. They are extracted from the META-INF folder of server.jar, which can be opened with a file archiving program that supports ZIP files. This extraction behavior can further be configured by a different main class available on the JAR file, see § Bundler options.

The server.jar also contains version.json file, which provides Java Edition version information.

Directory structure

Upon running the server.jar, the program generates the following resources:

Files are generated on the first run if not mentioned otherwise.

eula.txt

If an eula.txt file doesn't exist on startup, it is generated with default content and the program exits. The default content is as follows:

#By changing the setting below to TRUE you are indicating your agreement to our EULA (https://aka.ms/MinecraftEULA).
#[Generation time]
eula=false

Much like server.properties, it follows the .properties syntax. eula has to be set to true for the server to start.

Interface

The server software has both a command line interface and a rudimentary GUI.

The command-line interface outputs logs to the standard output, and accepts newline delimited input from the standard input, which is executed by the server as commands (similar to being executed by command blocks, but with the highest privilege level). Running a command in the interface does not require / at the beginning of the line.

The GUI appears if the platform supports windowing and the --nogui option is not provided. It is written in Abstract Window Toolkit (AWT), and it features three sections:

• "Stats" which displays memory usage as a graph and as a value, and average tick time,
• "Players" which displays a player list, and
• "Log and chat" which displays logs and serves the same function as the command-line interface.

Command-line options

Bundler options

The server.jar introduces an extra layer of code (called the "bundler") for extracting runtime libraries. This allows the main class to be specified at startup using system properties.

The following system properties can change the startup behavior:^[2]

• bundlerMainClass: Specifies the main class to start. If not specified, the main class defined on META-INF/main-class file in the server.jar (usually net.minecraft.server.Main) is used instead. There are three available main classes:
  • net.minecraft.server.Main: Used for launching the Minecraft server.
  • net.minecraft.data.Main: Used as entry point for data generators.
  • net.minecraft.gametest.Main: Used as an entry point for the GameTest framework, which provides its own command-line options.^[3]
  • Unspecified: If no option is specified or an empty blank string ("") is entered, it results in Empty main class specified, exiting.

Before executing the main class, the JAR file automatically extracts libraries and versions folders, even for unspecified option.

• bundlerRepoDir: Specifies the working directory for the resources extraction. If not specified, the current working directory is used instead.

System properties are specified like -D<property>, which property is the name defined above. They must be specified for the JVM program in the command-line, placed before -jar parameter (otherwise it will be specified for the server.jar file, which is invalid), e.g. java -DbundlerMainClass="net.minecraft.data.Main" -jar server.jar is a valid execution.

History

Issues

Issues relating to "Server.jar", "Server jar", or "Java server" are maintained on the bug tracker. Issues should be reported and viewed there.

References

See also

• Bedrock Dedicated Server, the server software used to host a Bedrock Edition server.
• client.jar, the program and resources for the Minecraft: Java Edition game.

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