WebSockets just receive onOpen and nothing more

FULL PRODUCT VERSION :
JDK 9-ea Build 164

ADDITIONAL OS VERSION INFORMATION :
Mac OS 10.11.7

A DESCRIPTION OF THE PROBLEM :
I just played around with the new HTTP/2 and WebSocket-API. Visting the page

https://www.websocket.org/echo.html

and wanted to convert the java script / html demo into java code.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Just start the programm

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
A sequence of

onOpen

onText

onClose
ACTUAL -
Just

onOpen

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.net.URI;
import java.nio.ByteBuffer;
import java.time.Duration;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

import jdk.incubator.http.HttpClient;
import jdk.incubator.http.WebSocket;
import jdk.incubator.http.WebSocket.MessagePart;

public class WebSocketExample
{
    public static void main(final String[] args) throws Exception
    {
        final URI uri = URI.create("ws://echo.websocket.org/");

        final WebSocket.Listener webSocketListener = new WebSocket.Listener()
        {
            @Override
            public void onOpen(WebSocket webSocket)
            {
                writeToScreen("onOpen");
                webSocket.request(1);
                System.out.println(webSocket);
                
                doSend(webSocket, "WebSocket rocks");
                System.out.println(webSocket);
            }

            @Override
            public CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason)
            {
                writeToScreen("onClose");
                return null;
            }

            @Override
            public CompletionStage<?> onText(WebSocket webSocket, CharSequence message, MessagePart part)
            {
                writeToScreen(message);
                return webSocket.sendClose();
            }

            @Override
            public void onError(WebSocket webSocket, Throwable error) {
                writeToScreen("ERROR: " + error.getMessage());
            }
            
            CompletionStage<?> doSend(WebSocket webSocket, CharSequence message)
            {
                writeToScreen("SENT: " + message);
                webSocket.sendText(message);
                return null;
            }

            void writeToScreen(CharSequence message)
            {
                System.out.println(message);
            }
        };

        final HttpClient client = HttpClient.newHttpClient();
        final WebSocket.Builder builder = client.newWebSocketBuilder(uri, webSocketListener);

        final CompletableFuture<WebSocket> websocketFuture = builder.connectTimeout(Duration.ofSeconds(5)).buildAsync();
        System.out.println("websocketFuture: " + websocketFuture);
        
        Thread.sleep(10000);
/*
        websocketFuture.exceptionally(e -> {
            System.out.println(e.getClass());
            return null;
        });
        
        Thread.sleep(2000);
        
        websocketFuture.thenAccept(action -> System.out.println("WS2: " + action));
        
        final WebSocket webSocket = websocketFuture.get();
        System.out.println("webSocket: " + webSocket);
        System.out.println("Connected");
        
        System.out.println("Sending Text");
        final CompletableFuture<WebSocket> asyncResponse1 = webSocket.sendText("Hello");

        System.out.println("Sending Ping");
        final ByteBuffer message = ByteBuffer.wrap("message".getBytes());
        final CompletableFuture<WebSocket> asyncResponse2 = webSocket.sendPing(message);

        System.out.println("Sending Binary");
        final CompletableFuture<WebSocket> asyncResponse3 = webSocket.sendBinary(message, true);

        System.out.println("Sending Close");
        final CompletableFuture<WebSocket> asyncResponseLast = webSocket.sendClose();
        
        Thread.sleep(5000);
        */
    }
}
---------- END SOURCE ----------

SUPPORT :
YES