If Rumba+ Desktop is your TN3270 emulator of choice the IDE launches it, if Rumba+ Desktop is not already running, and connects to the enterprise server where your application is running. Stopping debugging closes Rumba+ Desktop.
If Rumba+ Desktop is already running, when you start debugging, it opens a new tab and connects to the enterprise server where your application is running. In this case, stopping debugging does not close Rumba+ Desktop.