Since you mentioned USB-2-Serial conversion port, you can do a serial loopback test. It will display text only when it is connected to a specific port. All you need is a serial loopback port and follow the instructions from this link: http://zone.ni.com/devzone/conceptd.nsf/webmain/D48BA43C59B60277862569EE000501FD#6 This is not the simplest way in the world but hey it works!