WSMC

Enable Websocket support for Minecraft Java.
Since most CDN providers(at least for their free tier) do not support raw TCP proxy, with the help of this mod, the owner can now hide the server behind a CDN and let the players connect via WebSocket, thus preventing DDoS attacks.

For Minecraft Fabric:

• 1.20.5, 1.20.6
• 1.21, 1.21.1, 1.21.2, 1.21.3, 1.21.4, 1.21.5, 1.21.6, 1.21.7, 1.21.8

This mod runs standalone and does not have any dependency.

When this mod is installed on a server:

• The server would allow players to connect via WebSocket.
• Players can still join using vanilla TCP.
• The server accepts and handles TCP and WebSocket connections on the same listening port.
• Without installing this mod on the client side, a player can still join a server that has this mod using vanilla TCP.
• The server can acquire client statistics (e.g., real IP) from the WebSocket handshake..

When this mod is installed on a client:

• The client can join WebSocket-enabled servers using URI like ws@@hostname.com:port@path_to_minecraft_endpoint.
• The client can join any servers using vanilla TCP using the old syntax, e.g. hostname_or_ip:port.

Note

• This mod does not affect any gameplay.
• This mod does not modify any GUI.
• Vanilla clients can join your server even if you install this mod, note that other mods you have may prevent vanilla clients from joining.
• Installing this mod on your client does not prevent you from joining other vanilla or mod servers.
• The server can still get the real IP of the players who joined via CDN-proxied WebSocket.
• This mod is compatible with other TCP-WebSocket proxies, such as websocat.

Configuration

The configuration of this mod is passed in the "system properties". You can use -D in the JVM command line to pass such options.

Property Key	Type	Usage	Side	Default	Example
wsmc.disableVanillaTCP	boolean	Disable vanilla TCP login and server status.	Server	false	true
wsmc.wsmcEndpoint	string	Set the WebSocket Endpoint for Minecraft login and server status. If this property does not exist, a client can join the game via ANY WebSocket Endpoint. Must start with /, case-sensitive.	Server	Not set	/mc
wsmc.debug	boolean	Show debug logs.	Server Client	false	true
wsmc.dumpBytes	boolean	Dump raw WebSocket binary frames. Work only if wsmc.debug is set to true.	Server Client	false	true
wsmc.maxFramePayloadLength	integer	Maximum allowable frame payload length. Setting this value to your modpack's requirement else Netty will throw error "Max frame length of x has been exceeded".	Server Client	65536	65536

Dependencies

You need to install Fabric Loader and then install this mod. Fabric API is optional but highly recommended.

For developers

To modify and debug the code, first import the "fabric" folder as a Gradle project in Eclipse IDE, and then run the gradle task genEclipseRuns.

Windows users need to replace ./ and ../ with .\ and ..\, respectively.

The codebase uses Minecraft official mapping.

On the server side, if a client joins via WebSocket, its handshake request can be accessed via the vanilla net.minecraft.network.Connection class.
To obtain such information, cast a Connection instance into IConnectionEx, then calls IConnectionEx.getWsHandshakeRequest().

This is useful for obtaining information about the original request if the Minecraft server is behind a reverse proxy (e.g. a CDN).
For example, header X-Forwarded-For and CF-IPCountry indicate the client IP address and the client country code, respectively.

Compile artifact

git clone https://github.com/bfloat16/wsmc
cd wsmc/fabric
./gradlew build

To debug in Fabric, one may need to create run/config/fabric_loader_dependencies.json with the following content:

{
  "version": 1,
  "overrides": {
    "wsmc": {
      "-depends": {
        "minecraft": "IGNORED",
        "fabricloader": "IGNORED"
      }
    }
  }
} 

To specify JRE path:

./gradlew -Dorg.gradle.java.home=/path_to_jdk_directory <commands>

• Since 1.20.5, Minecraft requires Java 21