This is not related to JG but to the client-side HA-JNDI code i.e. the interface on which, the *client-side* and not server-side discover socket will be bound. It means that your client-side code runs on a multi-home machine, right?
This is not handled: it uses the default Interface. If you need this feature, please add a feature request on Sourceforge, I will do it when I have time.