@Override public DatagramSocketImpl createDatagramSocketImpl() { if (!isActive()) { String message = "Use " + NetworkRule.class.getName() + " to define DatagramSocket behaviour!"; LOGGER.log(Level.SEVERE, message); /* * check, if datagram socket is created in the scope of * a NetworkRule. */ throw new IOError(new SocketException(message)); } return super.createDatagramSocketImpl(); } });