Javax Websocket closing due to Illegal UTF-8 Sequence

问题

I'm writing a Websocket client in Java, using javax.websocket API, and org.glassfish.tyrus as the implementation.

Everything usually works, but sometimes, when I'm receiving very large strings, the connection closes with a mysterious 'Illegal UTF-8 Sequence' as the close reason.

log.info("Ws closed cuz: " 
   + reason.getCloseCode() + " , " 
   + reason.getReasonPhrase() + " , " 
   + reason.toString());

Output:

INFO: Ws closed cuz: NOT_CONSISTENT , Illegal UTF-8 Sequence ,
CloseReason[1007,Illegal UTF-8 Sequence]

I'm guessing that either the string was too large, or the string contained any characters which aren't UTF-8 compatible.

Is there a way to get any more info on the actual string / packet / frame which causes this issue? Or, if there's a way to tell tyrus to ignore any encoding issues and just pass me the raw string and let me handle it?

If not, is there another java websockets client which does the bare bones work of transmitting the strings over socket and doesn't do any validation, and just lets me handle the responses?

Appreciate any feedback.

回答1:

The following is just a guess.

(1) On the server side, the large string is split into one text frame and one or more following continuation frames. Technically, the original large string is converted into a byte array and then the byte array is split into multiple sub byte arrays. The sub arrays are set to frames one by one (= Each frame contains one sub byte array).

(2) Although there is no guarantee that each sub byte array is a valid UTF-8 sequence, validity check is performed either on the server side or on the client side. If so, it's a bug of Tyrus.

WebSocketListener of nv-websocket-client has callback methods in frame granularity such as onFrame, onTextFrame, onContinuationFrame and others (note that onTextMessage and onTextFrame are different), so you can examine the byte array of each frame there.

WebSocket websocket = new WebSocketFactory()
    .createSocket("ws://...")
    .addListener(new WebSocketAdapter() {
        @Override
        public void onFrame(WebSocket ws, WebSocketFrame frame) {
            // If the frame is a text frame with FIN bit cleared, or
            // if the frame is a continuation frame.
            if ((frame.isTextFrame() && frame.getFin() == false) ||
                frame.isContinuationFrame()) {
                // The payload of the frame. There is no guarantee
                // that this byte array is a valid UTF-8 sequence.
                byte[] payload = frame.getPayload();

                // Check whether the payload is a valid UTF-8 sequence
                // if you want to.
                checkPayload(payload);
            }
        }
    })
    .connect();

Why don't you use nv-websocket-client to examine what is happening in your WebSocket connection?

来源：https://stackoverflow.com/questions/32213497/javax-websocket-closing-due-to-illegal-utf-8-sequence