How to test multiplayer demo

1. Open Project Settings

1. Select the "Run" option

1. In the "Main Scene" choose the mp_demo.tscn which is in res://addons/inventory-system/demos/mp

1. Now in the "Debug" menu choose more than one instance to run

1. That's it, now it's enough to host the server and other clients connect, currently it is previously configured for a localhost connection.