Question

我有一个客户端应该从服务器下载一个用AES加密的图像文件（我不确定我是否正确实现了这一点）。但是，使用以下代码时，服务器会卡在“发送图像”打印消息上，而不会转到“完成”打印消息。换句话说，我无法下载图像文件。为什么会这样？

Server.java

public class Server { 

    public static void main (String [] args ) throws InvalidKeyException, IOException, Exception { 
        ServerSocket serverSocket = new ServerSocket(15123);
        Socket socket = null;
        //start of AES
        //Generate AES Key
        int sizeofkey = 128;
        KeyGenerator kg = KeyGenerator.getInstance("AES");
        //initialize with sizeofkey
        kg.init(sizeofkey);
        Key mykey = kg.generateKey();
        System.out.println("AES Key Generated");
        //create cipher object & initialize with generated key
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, mykey);

        while(true) {
            socket = serverSocket.accept();
            System.out.println("Accepted connection : " + socket.getRemoteSocketAddress().toString() + " <-> /127.0.0.1:15123" );

            OutputStream sos = socket.getOutputStream();

            // get the image from a webcam
            URL myimage = new URL("http://183.76.13.58:80/SnapshotJPEG?Resolution=640x480");

            //Picture in string format
            //String plainpic = null;

            //Picture in byte array format
            byte[] plainpic = null;
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            InputStream is = null;
            try {
                //in = new DataInputStream(myimage.openStream()); 



                is = myimage.openStream ();
                byte[] byteChunk = new byte[4096]; 
                int n;

                while ( (n = is.read(byteChunk)) > 0 ) {
                    baos.write(byteChunk, 0, n);
                }

                //Picture in string format
                //plainpic=Base64.getUrlEncoder().encodeToString(baos.toByteArray());

                //Picture in byte array format
                plainpic=baos.toByteArray();

            }     
            catch (Exception ee)    {
                System.out.println("Check internet connection please");
                socket.close(); 
                return;
            }
            byte[] cipherpic = cipher.doFinal(plainpic);

            DateFormat dateFormat = new SimpleDateFormat("yy/MM/dd HH:mm:ss");
            Date date = new Date();
            System.out.println("Sending image " + dateFormat.format(date));

            try {
                while (true) {
                    sos.write(cipherpic); 

                } 
            }
            catch (EOFException ee) { 
                System.out.println("-------------- Done ----------"); 
                is.close();
            }

            sos.flush();
            sos.close();
            socket.close();
    }

  } 
}

Client.java

public class Client { 
  public static void main(String [] args) throws IOException {
    String fname = "image.jpg";


    SSLSocket sslsocket = new Socket("127.0.0.1",15123);
    DataInputStream in = null;
    try{ in = new DataInputStream(sslsocket.getInputStream()); }
    catch (Exception ee)
    { System.out.println("Check connection please");
      sslsocket.close(); return;
    }
    FileOutputStream fos = new FileOutputStream(fname);

    try
    {
        while (true)
       fos.write(in.readByte());
    }
    catch (EOFException ee)
    {  System.out.println("File transfer complete");
       in.close();
    }
    fos.flush();
    fos.close();
    sslsocket.close();

    public static String asHex (byte buf[]) {

        //Obtain a StringBuffer object
        StringBuffer strbuf = new StringBuffer(buf.length * 2);
        int i;

        for (i = 0; i < buf.length; i++) {
            if (((int) buf[i] & 0xff) < 0x10)
                strbuf.append("0");
            strbuf.append(Long.toString((int) buf[i] & 0xff, 16));
        }
        // Return result string in Hexadecimal format
        return strbuf.toString();
    }
}

Answer 1

查看服务器中的内容：

        try {
            while (true) {
                sos.write(cipherpic); 

            } 
        }
        catch (EOFException ee) { 
            System.out.println("-------------- Done ----------"); 
            is.close();
        }

你永远不会得到EOFException，所以你永远在写cipherpic。

卡住从客户端发送文件到服务器

1 个答案: