private void parseRootElem(Element root, ServerConfig cfg) throws InvalidConfigurationException {
cfg.setInterface(evaluateXPathString("interface", root));
UntypedValue port = new UntypedValue(evaluateXPathString("port", root));
if (port.stringValue("").equals(""))
port = UntypedValue.NULL_VALUE;
checkInt(port, "port number", 1, 0xffff);
if (!port.equals(UntypedValue.NULL_VALUE))
cfg.setPort(port.intValue(ServerConfig.HTTP_PORT_DEFAULT));