code: @Override
      public synchronized ServerBootstrap newServerBootstrap() throws Exception {
  
          ServerSocketChannelFactory serverChannelFactory = this.serverChannelFactory;
  
          if (serverChannelFactory == null) {
              Executor bossExecutor = executorServiceFactory.newExecutorService("boss.server");
              NioServerBossPool bossPool = new NioServerBossPool(bossExecutor, 1);
              Executor workerExecutor = executorServiceFactory.newExecutorService("worker.server");
              NioWorkerPool workerPool = new NioWorkerPool(workerExecutor, 1);
              serverChannelFactory = new NioServerSocketChannelFactory(bossPool, workerPool);
  
              // unshared
              channelFactories.add(serverChannelFactory);
          }
  
          return new ServerBootstrap(serverChannelFactory) {
  
              @Override
              public ChannelFuture bindAsync(SocketAddress localAddress) {
                  return super.bindAsync(toInetSocketAddress(localAddress));
              }
  
          };
      }
docs: Returns a {@link ServerBootstrap} instance for the named transport.