public void unregister() throws IOException {
// When setting an empty GCM id, the Signal-Server also sets the fetchesMessages property to false.
// If this is the master device, other users can't send messages to this number anymore.
public void unregister() throws IOException {
// When setting an empty GCM id, the Signal-Server also sets the fetchesMessages property to false.
// If this is the master device, other users can't send messages to this number anymore.