流无法读取整个图像

Question

I am sending an image from java pc application to android application through sockets. My image that I send does not full read into the android byte[] for some reason and it has varying results for how much of the image is decoded. Here is my code

Desktop:

Socket socket = new Socket("127.0.0.1", 59900);
           // BufferedOutputStream bos = new BufferedOutputStream(socket.getOutputStream());

            OutputStream outputStream = socket.getOutputStream();

            Robot r = new Robot();
            Toolkit t = Toolkit.getDefaultToolkit();
            Rectangle rect = new Rectangle(t.getScreenSize());
            BufferedImage img = r.createScreenCapture(rect);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ImageIO.write(img, "jpg", baos);

            byte[] size = ByteBuffer.allocate(4).putInt(baos.size()).array();
            outputStream.write(size);
            outputStream.write(baos.toByteArray());
            //outputStream.flush();

            System.out.println("Flushed: " + System.currentTimeMillis());

            //Thread.sleep(12000);
            System.out.println("Closing: " + System.currentTimeMillis());
            socket.close();

Android code

 ServerSocket server = new ServerSocket(59900);
        Socket socket = server.accept();

        InputStream inputStream = socket.getInputStream();

        System.out.println("Reading: " + System.currentTimeMillis());

        byte[] sizeAr = new byte[4];
        inputStream.read(sizeAr);
        int size = ByteBuffer.wrap(sizeAr).asIntBuffer().get();
        byte[] imageAr = new byte[size];
        inputStream.read(imageAr);
       // ByteArrayInputStream bis = new ByteArrayInputStream(imageAr);

        bp = BitmapFactory.decodeByteArray(imageAr, 0, size);

Here is a picture of what the result looks like

Answer 1

As you're closing the socket after sending the image, you don't need to send the count, and therefore you don't need the ByteBuffer , the ByteArrayOutputStream , or the ByteArrayInputStream . Or the sleep. Get rid of them all and write the image directly to the socket output stream, and read it directly from the socket input stream with ImageIO.read() .

Answer 2

There is a common misconception that reading N bytes from a socket will return N bytes. A socket read call will return whenever it wants (usually when there is a time gap in the bytes received, which highly depends on the network). N is just the maximum number of bytes.

To solve this issue, you can either loop until you have the number of bytes required, or use specialized streams like DataOutputStream and DataInputStream , which offer the write() and readFully() method. They also provide the writeInt() and readInt() , that make sending the size easier.