Minecraft client running on port 4711?

I'm following this tutorial that says I should connect to Minecraft on port 4711. As far as I know the Minecraft server operates at port 25565.

Who am I connecting to? The Minecraft client?

PS. It actually says on the net that the Minecraft client may use port 4711 to communicate. Is this turned off for Minecraft on the Mac? My firewall is off but port 4711 seems unpopulated.

Solution 1:

Port 4711 is the RaspberryJuice Spigot server plugin's port to interface with Python.

When starting the server (Spigot) make sure to look through the startup messages and check that it loaded RaspberryJuice properly. I was trying to connect to that port from Python IDLE ide and got Connection Refused.

Turned out I had an error "major.minor 52" and had to update Java to the latest version to get Spigot to load RaspberryJuice properly.