code: protected String createServerUrl(String scheme, String host, Integer port) {
          StringBuilder sb = new StringBuilder();
          
          sb.append(scheme);
          sb.append("://");
          sb.append((host != null ? host : "localhost"));
          
          if (("http".equals(scheme) && port != 80) || ("https".equals(scheme) && port != 443)) {
              sb.append(":");
              sb.append(port);
          }
          
          return sb.toString();
      }
docs: helpful utilities for subclasses