MSMP Console

A server-side Fabric mod for Minecraft 1.21.11+ that extends the Minecraft Server Management Protocol (MSMP) by forwarding every server console log event to all connected WebSocket clients as a JSON-RPC 2.0 notification.

Requirements

• Minecraft 1.21.11+
• Fabric API 0.141.3+1.21.11+

Installation

1. Download the mod .jar and place it in your server's mods/ folder.
2. Enable the Management Server in server.properties:

   management-server-enabled=true

3. Start the server. The Management Server will listen on localhost:25576 by default.

Notification

Once a client connects to the WebSocket endpoint, it will receive a notification for every log event produced by the server.

Method: console:notification/log_event

Payload

Field	Type	Description
timestamp	string	ISO-8601 timestamp of when the log event occurred
level	string	Log level: TRACE, DEBUG, INFO, WARN, ERROR or FATAL
thread	string	Name of the thread that produced the log event
logger	string	Fully qualified name of the originating logger (e.g. the class name)
message	string	The fully interpolated log message
throwable	string	Serialized stacktrace if an exception was attached, omitted otherwise

Example

{
  "jsonrpc": "2.0",
  "method": "console:notification/log_event",
  "params": [{
    "timestamp": "2026-03-21T15:06:06.146Z",
    "level": "INFO",
    "thread": "Server thread",
    "logger": "net.minecraft.server.MinecraftServer",
    "message": "Done (1.019s)! For help, type \"help\""
  }]
}

{
  "jsonrpc": "2.0",
  "method": "console:notification/log_event",
  "params": [{
    "timestamp": "2026-03-21T15:06:07.212Z",
    "level": "ERROR",
    "thread": "Server thread",
    "logger": "net.minecraft.server.MinecraftServer",
    "message": "Encountered an unexpected exception",
    "throwable": "java.lang.NullPointerException: Cannot invoke ...\n\tat net.minecraft.server.MinecraftServer..."
  }]
}

How It Works

1. A custom Log4j2 appender is attached to the root logger on mod initialization, intercepting every log event produced by the server.
2. On SERVER_STARTED, the mod locates the internal ManagementServer instance via reflection.
3. For each log event, the appender builds a ConsoleLogPayload and broadcasts it to all active connections via Connection#sendNotification.
4. The notification is registered under the custom namespace console:notification/message using a Mixin accessor that bypasses the default minecraft: namespace restriction.

License

LGPL-3.0