for those interested
ethernet address 127.0.0.1 is reserved for use as the machine the application is running on. it allows different applications to connect to one another (different port #s) without needing to know the IP address of the machine they run on
i had thought something similar might be available on Windows for a com port, something 2 different applications could connect to for testing.
the application i was working on received information thru the com port from an arduino. i don't have the arduino hardware and thought a simple way to test would be to use a terminal emulator, a program that runs on a PC that allows you to tx/rx to a serial interface. if there was a virtual com port(s) (e.g. com99 and com100) both applications could be run and tested together using those ports.
since i run cygwin which provides a linux like environment, having a /dev/, i see a pty0 and a pty1. using those device names, i was able to open 2 terminal emulators on my PC and when i entered keypress on the one emulator, they appears on the other.
Term ls /dev/
clipboard console kmsg ptmx pty2 sda1 sda4 sdb1 ttyS3 zero
conin dsp mqueue pty0 random sda2 sda5 shm urandom
conout full null pty1 sda sda3 sdb tty windows
when i plug a USB device into my laptop, i see a something like /dev/ttyS3 appear.
so i believe Window can do this. not sure how; presumably which 2 com ports