Minecraft Relay Server (mcrelay)

A Minecraft reverse proxy server with server address rewrite.

Supports Minecraft servers and clients with version 12w04a and later (basically means release 1.2.1 and later).

Minecraft versions before 12w04a are NOT SUPPORTED!

Features

• Support reverse proxy for Minecraft servers by server address in the handshake packet which the client sends.
• Support rewrite server address and server port to camouflage a connection which uses an official server address (e.g., pretend to be a normal connection to Hypixel, avoiding their server address check).
• Support IP forwarding using HAProxy's Proxy Protocol (but it refuses any incoming connection using this protocol).

Requirements

• Linux
• libresolv.so (usually pre-installed)
• libcjson.so (on Debian-like systems, contained in package libcjson1)

Compatibility

Due to Minecraft handshake restrictions, this server supports:

• Game relay on server & client with version 12w04a and later, except version 12w17a, 13w41a and 13w41b.
• MOTD relay or MOTD status notice on server and client with version 1.6.1 and later, except version 13w41a and 13w41b.

Files

• CMakeLists.txt CMake configuration for compiling.
• doc Folder of documents.
• doc/information Informational documents.
• doc/information/loglevel.info Definitions of log levels.
• doc/information/versions.json Version manifest.
• doc/configuration Configuration examples.
• doc/configuration/logrotate Configuration used by logrotate.
• doc/configuration/mcrelay Configurations read by mcrelay itself.
• doc/configuration/systemd Configuration used by systemd, when using mcrelay as a service.
• src Folder of source codes.

Compile

Before compiling, you need to install cJSON at first.

For example, you can install it on Debian-like systems by apt install libcjson-dev.

Then you can use CMake to compile it by cmake -B build && cmake --build build, the executable file is build/mcrelay.

Additionally, if you want cross-compiling, the following CMake properties will be helpful:

• -DCMAKE_C_COMPILER: Specify an alternative compiler, CMake uses cc by default.
• -DEXEC_SUFFIX: Add a suffix to the final binary file, the file will be generated called mcrelay.

Usage

mcrelay <arguments|config_file>

Arguments
	-r / --reload:	Reload config on the running instance.
	-t / --stop:	Terminate the running instance.
	-f / --forking:	Makes the process become daemonized.
	-v / --version:	Show current mcrelay version.

The program will run as a non-exit-style program by default.

When using the -f or --forking option, the program will become daemonized, and store its main process's PID into /run/mcrelay/mcrelay.pid.

Config

See doc/configuration/mcrelay/config.jsonc for instructions.

Instructions for using DNS-based redirection (SRV)

If you are using an SRV record to provide your service, you should follow the instructions below.

Otherwise, your users will see a message about using an incorrect address to connect.

For example, your SRV record should be like this:

_minecraft._tcp.srvrecord.example.com. => PRIORITY WEIGHT PORT host.example.com

If you provide srvrecord.example.com to your user, you should set your virtual hostname in the configuration file as follows:

• For most Minecraft versions, use host.example.com.
• For Minecraft versions from 21w20a to 1.17, use srvrecord.example.com.

For compatibility, it's recommended to add both of them to your configuration.

IP Forwarding

You can provide the real client address and port through HAProxy's Proxy Protocol by this feature.

It's compatible with any server which supports this protocol (e.g. Bungeecord).

Bungeecord

To use this feature correctly, turn on the proxy_protocol in the config.yml (false to true).