docs: public void shutdown() {
          for (Client client : trackedClients) {
              // best effort closing -- ignores many problems
              try {
                  client.drain();
                  client.close();
              }
              catch (Exception e) {}
          }
          loaderClient = null;
  
          try {
              server.shutdown();
          } catch (InterruptedException e) {
              e.printStackTrace();
          }
          try {
              server.join(20000);
          } catch (InterruptedException e) {
              e.printStackTrace();
          }
      }