BufferUnderflowException？这里?

Question

我正在用Java编写一个小型UDP服务器。当服务器收到一个命令('GET_VIDEO')时，他读取一个文件('video.raw')，然后将它发送给客户端。

这是我的代码：

public class ServeurBouchon {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {

        byte[] buff = new byte[64];
        int port = 8080;
        DatagramPacket packet = new DatagramPacket(buff, buff.length);
        DatagramSocket socket = new DatagramSocket(port);

        System.out.println("Server started at 8080 ...");

        while (true) {
            socket.receive(packet);
            new ThreadVideo(socket, packet).run();
        }

    }

    public static class ThreadVideo extends Thread {

        private DatagramSocket socket;
        private DatagramPacket packet;

        public ThreadVideo(DatagramSocket socket, DatagramPacket packet) {
            this.packet = packet;
            this.socket = socket;
        }

        public void run() {
            String cmd = new String(packet.getData(), 0, packet.getLength());
            System.out.println("S:CMD reçu :" + cmd);
            if ("GET_VIDEO".equals(cmd)) {
                read_and_send_video(this.packet.getAddress());
            } else if ("TIMEOUT_REQUEST".equals(cmd)) {
                return;
            } else {
                System.out.println(" Exiting ...");
                return;
            }
            System.out.println("Fin .....");
        }

        private void read_and_send_video(InetAddress address) {
            System.out.println(" reading and sending video ...");
            File file = new File("./video/video.raw");
            ByteBuffer ibb = ByteBuffer.allocate(4);
            ibb.order(ByteOrder.BIG_ENDIAN);

            FileInputStream fis = null;
            DatagramPacket pack;
            byte[] buff = new byte[4];
            System.out.println(" Sending ...");
            try {
                fis = new FileInputStream(file);
                int size = 0;
                while ( size != -1) {
                    size = fis.read(buff, 0, buff.length);
                    System.out.println(" size = " + size);
                    ibb.put(buff);                  
                    System.out.println("Size : " + ibb.getInt());
                    int length = ibb.getInt();
                    byte[] fbuff = new byte[length];                    
                    fis.read(fbuff, 0, length);

                    pack = new DatagramPacket(fbuff, fbuff.length, address,
                            packet.getPort());
                    socket.send(pack);
                }

            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    }

}

原始文件格式是连续的“大小+帧”。"size“变量包含要读取的下一个帧的大小( int)。我的问题是当我读取文件时(在ibb.getInt())，行中，我得到了这个异常)：

Exception in thread "main" java.nio.BufferUnderflowException
at java.nio.Buffer.nextGetIndex(Buffer.java:480)
at java.nio.HeapByteBuffer.getInt(HeapByteBuffer.java:336)
at fr.sar.dss.bouchon.ServeurBouchon$ThreadVideo.read_and_send_video(ServeurBouchon.java:75)
at fr.sar.dss.bouchon.ServeurBouchon$ThreadVideo.run(ServeurBouchon.java:48)
at fr.sar.dss.bouchon.ServeurBouchon.main(ServeurBouchon.java:29)

也许我做错了，但是有人能告诉我我的错误在哪里吗？

(谢谢你的帮助;)

Answer 1

这上面写着两个国家。

System.out.println("Size : " + ibb.getInt());
int length = ibb.getInt();

用这个：

int length = ibb.getInt();
System.out.println("Size : " + length);

Answer 2

我终于找到了我的问题的答案。每次使用类ByteBuffer及其访问方法(如getInt()、getShort()、getFloat()、array())时，都应该调用该方法将当前缓冲区位置设置为零。此代码完全有效：

    System.out.println("Size : " + ibb.getInt());
    ibb.rewind();
    int length = ibb.getInt();
    ibb.rewind();

谢谢你的帮助