code: public void start() {
          // URL as configured takes precedence
          String configUrl = NetworkUtil.replaceExpression(config.getJolokiaConfig().get(ConfigKey.DISCOVERY_AGENT_URL));
          jolokiaHttpHandler.start(lazy,configUrl != null ? configUrl : url, config.getAuthenticator() != null);
  
          if (httpServer != null) {
              // Starting our own server in an own thread group with a fixed name
              // so that the cleanup thread can recognize it.
              ThreadGroup threadGroup = new ThreadGroup("jolokia");
              threadGroup.setDaemon(false);
  
              Thread starterThread = new Thread(threadGroup,new Runnable() {
              @Override
              public void run() {
                  httpServer.start();
              }
          });
              starterThread.start();
              cleaner = new CleanupThread(httpServer,threadGroup);
              cleaner.start();
          }
      }
docs: Start this server. If we manage an own HttpServer, then the HttpServer will
  be started as well.