I'm writing and attempting to test a Java class that can control communications between a master (or socket server) computer and client computers on the same LAN behind the same router. I copy ClientGUI.jar, an executeable jar, to my Mac Notebook but when I execute it apparently can't open port 6502 (which is not otherwise used). (It works on Linux machines but I don't have one to use as a second client to test multiple clients at present.)

I run the jar from terminal:

Java Code:
java -jar ClientGUI.jar
In System Preferences -> Security -> Firewall I can get to a list of Apps that can be selected to listen on ports but ClientGUI.jar is not recognized as an App which may be added to the list.

How may I open the port?