/**
* Utility method throwing an exception if the stack is not properly initialized.
*
* @throws java.lang.IllegalStateException if the underlying stack is not registered and
* initialized.
*/
private void assertConnected() throws IllegalStateException {
if (opSetPersPresence == null) {
throw new IllegalStateException(
"The provider must be signed on the service before" + " being able to communicate.");
} else opSetPersPresence.assertConnected();
}
