docs: @Handler(channels = NetworkChannel.class)
      public void onInput(
              Input<ByteBuffer> event, IOSubchannel netChannel)
              throws ProtocolException, InterruptedException {
          @SuppressWarnings("unchecked")
          final Optional<WebAppMsgChannel> appChannel
              = (Optional<WebAppMsgChannel>) LinkedIOSubchannel
                  .downstreamChannel(this, netChannel);
          if (appChannel.isPresent()) {
              appChannel.get().handleNetInput(event);
          }
      }