I'm curious if there is an app (or terminal commands) out there that will respond to certain port to let the other side know that the port is active? For example, I'm having a tough time trying to figure out if the router I'm using is at fault, or if there is some quirk in the system that's not allowing the data through. If I can have an application on Mac #1 (behind the router in question) that I can dial in a port to force the computer to respond to (even if there is no service that is asking for that port), that would be great. Then I can telnet the IP and port of Mac #1 from outside the network on Mac #2 to see if the router is forwarding the port correctly. It's doing other ports except this one (3306) so I'm trying to figure out what's going on. Thanks.