if ( ch == '[' ) {
                    String server = str.substring(mark, si).trim();
                    if ( server.length() == 0 ) {
                        // this can also be a v6 address within brackets, look ahead required
                        int nexts = str.indexOf('[', si + 1);
                        int nexte = str.indexOf(']', si);
                        if ( nexts >= 0 && nexte >= 0 && nexte == nexts - 1 ) {