I'm a programmer. Networking is not my specialty.
I need to allow programs I create (java C++), running on various computer (Windows, Linux) plugged into my router (my LAN), to send/receive UDP/TCP packets amongst themselves. Access Controls and Port Forwarding all seem to speak to communication with computers external to my network (i.e., the internet). I don't want allow protocols or open ports to/from computers on the internet. I only want to allow protocols and open ports between the computer plugged into my computer (my LAN)