How can I close a single port on the Port server that is using Real port

Hi, I need some help to close a connection on a single port that its using Realport, becasue when I use the IP address of the PortServer an the logical port to stablish a connection and I try to close it, it work, but when I´m using the real port to connect by selecting COM1 it doesn allow me to close it. I´m using it to make calls trough an analog modem with a RS232 protocol.

Go into task manager and force close the appliction. It sounds like it isn’t exiting ‘cleanly’. Its task name should still be there in the task manager.

If I do this all the others ports it will be also close, and this what I can not allow. So what else can I do without close the applications?