static void toggleMask(byte[] data, byte[] key) {
        for (int i = 0; i < data.length; i++) {
            data[i] = (byte) (data[i] ^ key[i % key.length]);
        }
    }
Used when an empty close frame was received (i.e., without a status code).
netbare-core/src/main/java/com/github/megatronking/netbare/ws/WebSocketProtocol.java