Server-In-Server

A Velocity plugin that launches and manages Minecraft server instances as child processes directly from the proxy. Configure servers in a single YAML file — the plugin handles starting, stopping, auto-restarting, port assignment, and proxy registration automatically.

How it works

When Velocity starts, the plugin reads plugins/server-in-server/config.yml. For each configured server with auto-start: true, it spawns a new Java process running the specified server jar, generates server.properties with the correct port, optionally accepts the EULA, registers the server in Velocity's proxy, and adds it to velocity.toml. If a server crashes, the plugin can auto-restart it a configurable number of times.

Quick start

1. Place the plugin jar in plugins/
2. Start Velocity — the plugin creates plugins/server-in-server/config.yml with a default config
3. Edit config.yml to match your server jars and settings
4. Run /sis reload in the Velocity console to apply changes

Configuration

Global settings

auto-eula: false
lobby-server: "lobby"

Field	Default	Description
auto-eula	false	If true, creates eula.txt with eula=true automatically for every server. If false, you must accept the EULA manually.
lobby-server	""	Server name to connect players to when they first join the proxy. Leave empty to disable.

Server entries

servers:
  - name: "lobby"
    jar: "servers/lobby/server.jar"
    directory: "servers/lobby"
    port: 0
    flags: "-Xmx1G -Xms512M"
    auto:
      start: true
      restart: true
      retry-count: 0
    stop:
      command: "stop"
      wait-to-stop: true
      wait: 10

Field	Default	Description
name	—	Server name used in Velocity and for routing
jar	—	Path to the server jar (relative to the proxy directory, or absolute)
directory	"servers/<name>"	Working directory for the server process
port	0	Server port. 0 = auto-assign (velocityPort + 2 + index)
flags	"-Xmx1G -Xms512M"	JVM arguments passed to java before -jar
auto.start	true	Start this server when Velocity (re)starts
auto.restart	false	Restart the server automatically when it stops/crashes
auto.retry-count	0	Max restart attempts. 0 = infinite restarts
stop.command	"stop"	Command sent via stdin to gracefully stop the server
stop.wait-to-stop	true	If true, wait for the process to exit before force killing
stop.wait	10	Seconds to wait before force killing (only if wait-to-stop is true)

Commands

All commands use the /sis prefix and can be run from the Velocity console or by players with appropriate permissions.

Command	Description
/sis start <server>	Start a configured server
/sis stop <server>	Gracefully stop a running server
/sis restart <server>	Stop then start a server
/sis forcestop	Kill all child processes and shut down Velocity
/sis reload	Reload config, stop all servers, start auto-start ones
/sis list	Show all configured servers with their status and ports
/sis com <server> <command>	Send a console command to a running server

Port auto-assignment

If port is 0, the plugin calculates it as:

port = velocityBindPort + 2 + serverIndex

Where serverIndex is the server's position in the servers list (0-based).

Example with Velocity on port 25565:

Index	Server	Calculated port
0	lobby	25567
1	survival	25568
2	creative	25569

velocity.toml integration

On every startup and reload, the plugin scans velocity.toml for the [servers] section and adds or updates entries for all configured servers. Existing entries for other servers are preserved. If the [servers] section does not exist, it is created at the end of the file.

Requirements

• Java 21+
• Velocity 3.5.0-SNAPSHOT (or compatible 3.x)