code: @Handler(channels = NetworkChannel.class)
      public void onClosed(Closed event, TcpChannel netConnChannel) {
          netConnChannel.associated(WebAppMsgChannel.class).ifPresent(
              appChannel -> appChannel.handleClosed(event));
          pooled.remove(netConnChannel.remoteAddress(), netConnChannel);
      }
docs: Called when the network connection is closed.
  
  @param event the event
  @param netConnChannel the net conn channel