The monitor allows you to view live matches and replays in your browser.
Start the server with the --monitor 8000 flag and navigate to
http://localhost:8000/ in your browser.
Start the monitor and provide a path to a replay directory.
Usage:
java -jar monitor/monitor-[version]-with-dependencies.jar [--port PORT] <server/replays/path>
Then navigate to http://localhost:8000/?/ (or similar) in your browser.