如何通过java中的套接字发送图像? [英] How to send images through sockets in java?

问题描述

我正在编写一个客户端-服务器程序，我希望它发送一个图像.代码如下:

I am writing a client-server program and I want that to send an image. The code is the following:

//RECEIVER
while(true){
  try{
            socket = server.accept();

            out = new ObjectOutputStream(socket.getOutputStream());
            out.flush();
            in = new ObjectInputStream(socket.getInputStream());

            System.out.println("Connected to "+PORTA+".");

            while(!socket.isClosed()){ 
                System.out.println("\nPrint the action");
                azione = reader.readLine();

           if(azione.equals("screenshot")){

                    out.writeObject("screenshot");
                    out.flush();
                    BufferedImage screenshot = ImageIO.read(in);

                    ImageIO.write(screenshot, "jpg", new File("screenshot.jpg"));
                }
  }catch(Exception ex){
            System.out.println("Not connected.\n");
  } 
}

和服务器:

while(true){ 
   try{
            socket = new Socket(INDIRIZZO, PORT);

            out = new ObjectOutputStream(socket.getOutputStream());
            out.flush();
            in = new ObjectInputStream(socket.getInputStream());

            while(!socket.isClosed()){
                try {
                  action = (String)in.readObject();
                  if(azione.equals("screenshot")){
                        BufferedImage screenshot = new Robot().createScreenCapture(new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()));
                        ImageIO.write(screenshot, "jpg", out);
                    }catch(Exception e){

                    }
            }
   }catch(Exception ex){
      //
   }
}

我的问题是只有当我关闭套接字或输出流时客户端才会收到图像，但我不希望这种情况发生.我怎样才能绕过它?如何将图像作为字节发送?谢谢！

My problem is that the client receive the image only if I close the socket or the out stream, but I don't want that to happen. How can I bypass that? How can I send the image as bytes? Thanks!

推荐答案

问题在于 ImageIO.read 等待流结束.套接字仅在您关闭它时发送它.(这是有道理的)

The problem is that ImageIO.read waits for the end of the stream. Sockets send it only when you close it. (which makes sense)

您要做的是首先发送图像的大小，然后在接收方将图像作为字节数组读取.

What you want to do is to first send size of the image and on the receiver side to read the image as byte array.

public class Send {

    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 13085);
        OutputStream outputStream = socket.getOutputStream();

        BufferedImage image = ImageIO.read(new File("C:\\Users\\Jakub\\Pictures\\test.jpg"));

        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        ImageIO.write(image, "jpg", byteArrayOutputStream);

        byte[] size = ByteBuffer.allocate(4).putInt(byteArrayOutputStream.size()).array();
        outputStream.write(size);
        outputStream.write(byteArrayOutputStream.toByteArray());
        outputStream.flush();
        System.out.println("Flushed: " + System.currentTimeMillis());

        Thread.sleep(120000);
        System.out.println("Closing: " + System.currentTimeMillis());
        socket.close();
    }
}


public class Receive {

    public static void main(String[] args) throws Exception {
        ServerSocket serverSocket = new ServerSocket(13085);
        Socket socket = serverSocket.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);

        BufferedImage image = ImageIO.read(new ByteArrayInputStream(imageAr));

        System.out.println("Received " + image.getHeight() + "x" + image.getWidth() + ": " + System.currentTimeMillis());
        ImageIO.write(image, "jpg", new File("C:\\Users\\Jakub\\Pictures\\test2.jpg"));

        serverSocket.close();
    }

}

这篇关于如何通过java中的套接字发送图像?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！