java - 通过java套接字下载图像时需要编码规范吗？

Question

该程序应该从闪烁中下载指定的图像。这是一个家庭作业问题，我必须使用套接字。我的程序成功发出 http 请求并收到响应。我消除了 header 并将字节写入 jpg 文件。但是当我想用图像查看器程序打开它时，它说:

Error interpreting JPEG image file(Improper call to JPEG library in state 200

所以我单独下载了图像并在文本编辑器中打开，看起来它的某些部分没有转换。

原始文件:

\FF\D8\FF\E0\00JFIF\00\00\00\00\00\00\FF\E2\A0ICC_PROFILE

下载的文件:

ￜￜￜￜ\00JFIF\00\00\00\00\00\00ￜￜￜICC_PROFILE

这与字符编码有关吗？如果是，我应该如何指定编码？或者我应该怎么做才能真正获得jpeg文件？

public class ImageReceiver {
public static void main(String[] args) {
    String imglink = "https://farm2.staticflickr.com/1495/26290635781_138da3fed8_m.jpg";
    String flicker = "farm2.staticflickr.com";

    Socket socket = null;
    DataOutputStream out;

    try {
        socket = new Socket(flicker, 80);
        out = new DataOutputStream(socket.getOutputStream());

        out.writeBytes("GET "+ imglink +" HTTP/1.1\r\n");
        out.writeBytes("Host: "+ flicker +":80\r\n\r\n");
        out.flush();
    } catch (IOException e) {
        e.printStackTrace();
    }

    DataInputStream in = null;
    OutputStream output = null;

    try {
        in = new DataInputStream(socket.getInputStream());
        output = new FileOutputStream("chair.txt");

        System.out.println("input connection is established");

        byte[] bytes = new byte[2048];
        int length;    
        boolean eohFound = false;

        while ((length = in.read(bytes)) != -1) {
            if(!eohFound){
                String string = new String(bytes, 0, length);
                int indexOfEOH = string.indexOf("\r\n\r\n");
                if(indexOfEOH != -1) {
                    System.out.println("index: " + indexOfEOH);
                    length = length - indexOfEOH - 4;
                    System.out.println(length);
                    bytes = string.substring(indexOfEOH + 4).getBytes();
                    eohFound = true;
                } else {
                    length = 0;
                }
            }
            output.write(bytes, 0, length);
            output.flush();
        }
    } catch (IOException e) {
        e.printStackTrace();
    } 


    try {
        in.close();
        output.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

    System.out.println("Image is downloaded");

}

}

Answer 1

在EJP的帮助下，我重写了我的代码。这里只修改了部分。我 readLine() 直到得到新行，然后我读取字节并写入文件:

    try {
        in = new DataInputStream(socket.getInputStream());
        output = new FileOutputStream("chair.jpg");

        byte[] bytes = new byte[2048];
        int length;

        String inputLine;

        //Get rid of headers...
        while ((inputLine = in.readLine()) != null){
            if(inputLine.equals(""))
                break;
        }


        while ((length = in.read(bytes)) != -1) {
            output.write(bytes, 0, length);
            output.flush();
        }

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