How to make Firewall work without GUI?

Product: CFP 3.9.81003.508
How to make Firewall and Defense+ (Antivirus not needed) work without GUI (I means that tray icon, not the popup alerts) ? I am using a rather old computer, so it’s quite important to save memory. It seems Firewall does not work without cfp.exe launched. (I never understand what is that cmdagent.exe is working for.)

Forgive me if the questions sounds silly…

The GUI is cfp.exe. The firewall will work with the cfp.exe switched off.

Make sure you have all rules in place when working without the GUI. Also consider how you want to use D+. It can be set to Block all the unknown requests when the application is closed (D+ → Advanced → Defense + settings). It is not possible to use command line to instruct the firewall.