I told him you can login using the rdp window and it will let you know or check the port to make sure it's open. His reply was no no what if it was from a windows to a Linux how would you rdp? Well you can't it's a windows thing you would ssh. He said no the answer he was looking for was ping... why didn't you ask how do you test if two entities are connected or if 2 computers of different OS can see each other?