NanoLimbo

This is a lightweight Minecraft limbo server, written in Java with Netty. The main goal of this project is maximum simplicity with a minimum number of sent and processed packets. The limbo is empty; there is no ability to set a schematic building since this is not necessary. You can send useful information via chat or boss bar.

The server is fully clear. It is only able to keep a lot of players while the main server is down.

General features:

• High performance. The server doesn't save or cache any useless (for limbo) data.
• Doesn't spawn threads per player. Use a fixed thread pool.
• Support for BungeeCord and Velocity info forwarding.
• Support for BungeeGuard handshake format.
• Support for MiniMessage text format.
• Multiple versions support.
• Fully configurable.
• Lightweight. App size around 5MB.

Versions support

Symbol X means all minor versions.

• 1.7.X
• 1.8.X
• 1.9.X
• 1.10.X
• 1.11.X
• 1.12.X
• 1.13.X
• 1.14.X
• 1.15.X
• 1.16.X
• 1.17.X
• 1.18.X
• 1.19.X
• 1.20.X
• 1.21.X   (incl. 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11)
• 26.1.X

The server doesn't support snapshots.

Commands

• help - Show help message
• conn - Display number of connections
• mem - Display memory usage stats
• version - Display limbo version
• stop - Stop the server

Note that the server also will be closed correctly if you just press Ctrl+C.

Installation

Required software: JRE 17+

The installation process is simple.

1. Download the latest version of the program here.
2. Put the jar file in the folder you want.
3. Create a start script as you did for Bukkit or BungeeCord, with a command like this: java -jar NanoLimbo.jar
4. The server will create settings.yml file, which is the server configuration.
5. Configure it as you want and restart the server.

Player info forwarding

The server supports player info forwarding from the proxy. There are several types of info forwarding:

• LEGACY - The BungeeCord IP forwarding.
• MODERN - Velocity native info forwarding type.
• BUNGEE_GUARD - BungeeGuard forwarding type.

If you use BungeeCord, or Velocity with LEGACY forwarding, just set this type in the config.
If you use Velocity with MODERN info forwarding, set this type and paste the secret key from Velocity config into secret field. If you installed BungeeGuard on your proxy, then use BUNGEE_GUARD forwarding type. Then add your tokens to tokens list.

Credits

This release is built on top of community contributions across multiple forks. Huge thanks to everyone listed below — expand each section to see what they contributed.

Nan1t — original author & maintainer

The entire foundation of NanoLimbo:

• Netty pipeline, packet system, multi-version protocol skeleton up to 1.21
• BungeeCord and Velocity info forwarding
• Configuration framework, command system, dimension registry
• Project structure, build setup, release process

Source: https://github.com/Nan1t/NanoLimbo

BoomEaro (Valentine) — Minecraft 1.21.2 → 26.1, modernization

The bulk of post-1.21 protocol work and toolchain modernization:

• Protocol support for 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8, 1.21.9, 1.21.10, 1.21.11 and 26.1
• Rewrote the login → configuration phase for the post-1.20.5 known-packs handshake: PacketKnownPacks, PacketUpdateTags, per-version PacketRegistryData
• Rewrote play packets for the 1.21.x line: PacketLogin (formerly PacketJoinGame), PacketChunkWithLight (real heightmaps + biome palette + light update), PacketPlayerPositionAndLook for the 1.21.2 teleport-flags redesign, PacketGameEvent with start_waiting_for_chunks
• Build modernization: Gradle Kotlin DSL, version catalog, Java 17, Lombok, GitHub Actions for build & release
• Adventure stack (api / gson / legacy / plain / json / nbt) + MiniMessage support in all text fields
• Netty 4.2 split modules with native transports: epoll, io_uring (Linux x86_64 / aarch64) and kqueue (macOS x86_64 / aarch64); new TransportType enum
• Per-connection traffic rate limiting in ChannelTrafficHandler
• Refactored configuration serializers, VersionedDimension, version command

Source: https://github.com/BoomEaro/NanoLimbo  ·  upstream PR: #98

YueMi-Development — external secret files

• @-prefix support in infoForwarding.secret and infoForwarding.tokens: values starting with @ are read from a file relative to the working directory. Lets you keep credentials out of settings.yml (Docker / Kubernetes secrets, SOPS, etc.).

Source: https://github.com/YueMi-Development/NanoLimbo

Biquaternions — IP logging privacy switch

• New logPlayersIp config flag. When false, player IP addresses are redacted in connection logs (shown as <redacted>). Useful for GDPR / privacy-compliant deployments.

Source: https://github.com/Biquaternions/NanoLimbo  ·  upstream PR: #96

Contributing

Feel free to create a pull request if you find some bug or optimization opportunity, or if you want to add some functionality that is suitable for a limbo server and won't significantly load the server.

Building

Required software:

• JDK 17+
• Gradle 9+ (optional)

To build a minimized jar, go to the project root directory and run in the terminal:

./gradlew build

Contacts

If you have any questions or suggestions, join our Discord server!