Difference between GetPortNames and Isopen

http://msdn.microsoft.com/en-us/library/system.io.ports.serialport.isopen(v=vs.110).aspx[^]

The IsOpen documentation states, "The IsOpen property tracks whether the port is open for use by the caller, not whether the port is open by any application on the machine."

I guess you'll need to find another way to tell.

I know with UDP ports, years ago, the only way I could tell if they were in use was to try and open one and if I got an exception it meant another app had it open. Perhaps serial ports have something similar.