MCServerNap

A lightweight, serverless Minecraft server watcher and auto-starter.

Overview

mcservernap monitors incoming Minecraft client connections and automatically launches (and later stops) a local Minecraft server process via RCON. It enables you to avoid running your server 24/7 by:

Listening for the first legitimate Minecraft LoginStart handshake.
Spinning up the server process on-demand when a player attempts to join.
Watching the server via RCON for player activity.
Stopping the server after an idle timeout.

There is also a stop subcommand to immediately send a /stop command via RCON.

Features

On-demand startup: server only runs when a player actually joins.
Idle shutdown: automatically stops server when no players remain for a set duration.
Cross-platform: spawns a new terminal window on Windows, runs directly on Linux systems.
Extensible: configure RCON settings, startup command and ports.

Installation

Ensure you have Rust and Cargo installed (see rustup.rs).
Clone this repository:

git clone https://github.com/yourusername/MCServerNap.git
   cd MCServerNap

Build the binary:

cargo build --release

The executable can be found under target/release/mcservernap.exe

(Optional) If you wish to install globally:

cargo install --path .

Usage

mcservernap <COMMAND> [OPTIONS]

Subcommands

listen — Listen for incoming connections and start the server on first join.
stop — Immediately send a /stop command via RCON to shut down an already-running server.

`listen` Options

| Option | Description | Required | | --------------- | ---------------------------------------------------------------------- | -------- | | host | Host or IP to bind (e.g. 0.0.0.0) | Yes | | port | Port to listen on for Minecraft clients | Yes | | cmd | Command or script to launch the Minecraft server | Yes | | args... | Arguments passed to the server command | No | | --server-port | Port of the actual Minecraft Server that users will get forwarded to | Yes | | --rcon-port | Port for the server’s RCON interface | Yes | | --rcon-pass | Password for RCON authentication | Yes |

[!IMPORTANT]

When not using a script and instead executing a command with its own arguments, you need to append the command to the end of the line followed by -- and all the arguments of the command. See below for an example!

[!NOTE]

The port of the Minecraft server does not require port forwarding, only the port of this application.

Example

mcservernap listen 0.0.0.0 25565 --server-port 25566 --rcon-port 25575 --rcon-pass rconpasswordmeow java -- -Xmx5G -Xms5G -jar server.jar nogui

Script Example

mcservernap listen 0.0.0.0 25565 "C:\path\to\your\script\start_server.bat" --server-port 25566 --rcon-port 25575 --rcon-pass rconpasswordmeow

IMPORTANT: When using a script, make sure the script closes its window at the end of the script (Windows .bat example: exit), or else this application won't detect that the Minecraft server process has shut down!

Once a client sends a LoginStart packet, the tool:

Drops the listener and launches your server command.
Starts an idle watchdog task that polls RCON according to rconpollinterval.
If no players remain for the defined amount of rconidletimeout time, sends /stop and exits.

`stop` Options

| Option | Description | Required | | ------------- | ------------------------------------ | -------- | | --rcon-port | Port for the server’s RCON interface | Yes | | --rcon-pass | Password for RCON authentication | Yes |

Example

mcservernap stop --rcon-port 25575 --rcon-pass rconpasswordmeow

This immediately connects via RCON and sends the /stop command.

Configuration & Environment

Logging: Controlled via entry point of `main()`:

envlogger::Builder::fromdefault_env()
        .filter_level(log::LevelFilter::Info) // Change this LevelFilter to change logging level (e.g. Debug)
        .init();

You need to rebuild the project for the change to take effect.

The configuration will be generated on first time usage of this application under `config/cfg.toml`

Configuration Options:

Timeouts & Intervals: set via rconidletimeout and rconpollinterval in seconds
Message of the day (MOTD): The message shown to the user in the server browser menu. set via motdtext, motdcolor and motd_bold
Connection Message: The message shown to the user when they try to connect. Set via connectionmsgtext, connectionmsgcolor and connectionmsgbold
Server Icon: The icon of the server within the server browser menu. Set by inserting a .png file in the config/ folder with the name server-icon.png. The image must be 64x64 pixels big. If it's not, this application will automatically resize the image to meet this requirement
Configuration Directory: The location of the cfg.toml can be changed from the standard config/ directory by editing the value of configdirectoryname. This will delete the previous directory and move the files to the new one