WebSocket throws exception when client disconnects

[wyvx]

I have a simple websocket server. A client can connect and it behaves correctly, until the client disconnects. Then, Helidon throws an Internal Error exception.

Environment Details

• Helidon Version: 4.0.0
• Helidon SE or Helidon MP: Helidon SE
• JDK version: 21
• OS: macOS Ventura 13.6
• Docker version (if applicable): None

---

Problem Description

I have a simple websocket server. I use websocat (https://github.com/vi/websocat) to test as a client. It connects and it behaves correctly, until the client disconnects (Ctrl+C websocat). Then, Helidon throws an Internal Error exception.
This problem is easily reproducible and it happens every time.

This is the stack trace on my program, the server, after I exit the websocket client:

  io.helidon.http.RequestException: Internal error
  io.helidon.http.RequestException$Builder.build(RequestException.java:139)
  io.helidon.webserver.http1.Http1Connection.handle(Http1Connection.java:202)
  io.helidon.webserver.ConnectionHandler.run(ConnectionHandler.java:155)
  io.helidon.common.task.InterruptableTask.call(InterruptableTask.java:47)
  io.helidon.webserver.ThreadPerTaskExecutor$ThreadBoundFuture.run(ThreadPerTaskExecutor.java:239)
  java.base/java.lang.VirtualThread.run(VirtualThread.java:311)
  Cause: io.helidon.common.buffers.DataReader$InsufficientDataAvailableException
  io.helidon.common.buffers.DataReader.pullData(DataReader.java:83)
  io.helidon.common.buffers.DataReader.ensureAvailable(DataReader.java:111)
  io.helidon.common.buffers.DataReader.read(DataReader.java:123)
  io.helidon.websocket.AbstractWsFrame.readFrameHeader(AbstractWsFrame.java:83)
  io.helidon.websocket.ClientWsFrame.read(ClientWsFrame.java:125)
  io.helidon.webserver.websocket.WsConnection.readFrame(WsConnection.java:247)
  io.helidon.webserver.websocket.WsConnection.handle(WsConnection.java:107)
  io.helidon.webserver.http1.Http1Connection.handle(Http1Connection.java:160)
  io.helidon.webserver.ConnectionHandler.run(ConnectionHandler.java:155)
  ... (3 more)

Steps to reproduce

I have a simple websocket built like so:

WebServer.builder()
    .port(3000)
    .addRouting(WsRouting.builder().endpoint("/yapper", new WsListener() {
        @Override
         public void onMessage(final WsSession session, final String text, final boolean last) {
             System.out.printf("msg: %s, last: %b%n", text.trim(), last);
             session.send("yap!", true);
         }
    }))
    .build()
    .start();            

In a separate terminal I run:

./websocat ws://localhost:3000/yapper -t -

I can say "hi" and it replies with "yap!". My program prints "hi".
I can say "something else" and it replies with "yap!". My program prints "something else".
I then do Ctrl+C on websocat. websocat exits. My program throws the exception above.
Notice in the stack trace no line corresponds to my own code. It's all internal Helidon code.