Most of the ways that EnhancedIOException gets thrown is because the enhanced IO module isn't plugged in to the driver station computer. You should think about what you want the code to do in that case and put that in the catch block. You probably want to turn the relay off, but you may want to do something else like send status back to the driver station.
If you're not familiar with exceptions, there is a java tutorial about them.
http://docs.oracle.com/javase/tutori...al/exceptions/