Here's the code:

@WebServlet(urlPatterns = "/upgrade")
public class UpgradeServlet extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    if ("upgrade".equalsIgnoreCase(req.getHeader("Connection"))) {
      req.upgrade(EchoHandler.class);
    }
  }
}

public class EchoHandler implements HttpUpgradeHandler {
  @Override
  public void init(WebConnection wc) {
    try {
      ServletInputStream in = wc.getInputStream();
      ServletOutputStream out = wc.getOutputStream();
     
      BlockingQueue<String> queue = new LinkedBlockingQueue<String>();
      in.setReadListener(new EchoReadListener(queue, in));
      out.setWriteListener(new EchoWriteListener(queue, out));
    } catch (IOException e) {
      throw new IllegalStateException(e);
    }
  }

public class EchoReadListener implements ReadListener {
  @Override
  public void onDataAvailable() throws IOException {
    while (in.isReady()) {
      int length = in.read(buffer);
      String input = new String(buffer, 0, length);
      if (false == queue.offer(input)) {
        System.err.println("'" + input + "' input was ignored");
      }
    }
  }

which means that from now on the protocol between my telnet client and WF is pure TCP.

So, I start typing some text, hit Enter and.... nothing happens. onDataAvailable() is NEVER called. More so, this makes WF totally irresponsive - my whole webapp is dead.

I believe, I'm doing something wrong - any ideas what exactly? There is also a slight chance that Upgrade feature in WF is f****d :)
Anyway, WF should not block even in case my upgraded protocol is not working correctly?

Many thanks,
Przemyslaw