public synchronized ORB getInstance(String initialHost, int initialPort) {
        if (orb_ == null) {
            Properties props = new Properties();
            props.put("com.sun.CORBA.POA.ORBPersistentServerPort",
                    Integer.toString(initialPort));
            props.put("com.sun.CORBA.POA.ORBPersistentServerHost",
                    initialHost);
            orb_ = ORB.init((String[]) null, props);
        }
        return orb_;
    }