@WillR:
That works to change the server IP address. I wanted to be able to program the client IP address also. The boxes I'm designing have to be reconfigurable in the field. You can't create an instance of Client within the setup code.
@zoomkat:
Thanks. That looks interesting. I didn't find it with a day of googling.
As a final note on this, it works. I can now have a setup routine that changes all the ethernet parameters in my setup structure, save it to EEPROM and always load those values on power up.
I still have to figure out how to read the hex characters for the MAC address from the console and convert them, but that is fairly straightforward.