通过套接字从Java向CPP发送屏幕截图-发出接收图像

Java（服务器）:

截图方法

    //Take screenshot of active application
    robot.keyPress(KeyEvent.VK_CONTROL);
    robot.keyPress(KeyEvent.VK_ALT);
    robot.keyPress(KeyEvent.VK_PRINTSCREEN);
    robot.delay(5);
    robot.keyRelease(KeyEvent.VK_PRINTSCREEN);
    robot.keyRelease(KeyEvent.VK_CONTROL);
    robot.keyRelease(KeyEvent.VK_ALT);
    Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
    flavors = cb.getAvailableDataFlavors();
    for (DataFlavor flavor : flavors) {
        if (flavor.toString().indexOf("java.awt.Image") <= 0) {
            continue;
        }
        i[0] = (Image) cb.getData(flavor);
    }
    robot.delay(50);
    bi = new BufferedImage(i[0].getWidth(null), i[0].getHeight(null),
            BufferedImage.TYPE_BYTE_GRAY); // keep buffered image as gray scale
    // resize image since I don't need large res
    resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, BufferedImage.TYPE_BYTE_GRAY);
    g = resizedImage.createGraphics();
    g.drawImage(i[0], 0, 0,IMG_WIDTH, IMG_HEIGHT, null);
    g.dispose();
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); // <-- This is irrelevant!
    ImageIO.write(resizedImage, "jpg", baos);
    baos.flush();
    byte[] imageInByte = baos.toByteArray();
    baos.close();
    return imageInByte;

打开套接字并发送图像

    byte[] screenShot = SaveScreenshot();
    ServerSocket serverSocket = null; 
    Socket slientSocket = null;
    Socket clientSocket = null;
    try {
        serverSocket = new ServerSocket(4447);
        clientSocket = serverSocket.accept();

OutputStreamWriter（clientSocket.getOutputStream（））；

        OutputStream out = clientSocket.getOutputStream();
        ByteArrayOutputStream bScrn = new ByteArrayOutputStream();
        out.write((Integer.toString(screenShot.length)).getBytes());
        out.write(screenShot,0,screenShot.length);
        serverSocket.close();
        clientSocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }

CPP（客户）：

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <cstdio>
#include <cstddef>
#include <cstdlib>
#include <strings.h>

using namespace std;
int main()
{
int sockfd; // socket file descriptor 
int portno; // port number
struct sockaddr_in serv_addr;
struct hostent *server;
char ip[] = "127.0.0.1"; // ip of server
portno = 4447; // port number
sockfd = socket(AF_INET, SOCK_STREAM, 0); // generate file descriptor 
if (sockfd < 0)
    perror("ERROR opening socket");
server = gethostbyname(ip); //the ip address (or server name) of the listening server.
if (server == NULL) {
    fprintf(stderr,"ERROR, no such hostn");
    exit(0);
}
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0)
    perror("ERROR connecting");
char rbuff[256];
//int rbuff;
int rbytes;
rbytes = recv(sockfd, rbuff, sizeof(rbuff), 0); // similar to read(), but return -1 if socket closed
rbuff[rbytes] = ''; // set null terminal
printf("Message: %s  %dn", rbuff, atoi(rbuff));
unsigned char *ssByte = new unsigned char[atoi(rbuff)];
rbytes = recv(sockfd, ssByte, sizeof(ssByte), 0);
FILE *fp=fopen("/home/chen/Pictures/recv.jpeg","w");
fwrite(ssByte,sizeof(ssByte),1, fp);
return 0;
}

1. Java打开套接字
2. Cpp连接
3. Java发送ByteArray大小（int）
4. Cpp创建大小为的无符号char*数组
5. Java发送图像
6. Cpp尝试保存

确保使用Java，保存图像，一切顺利。检查了我从Java接收到Cpp的图像的大小是否在两者之间相同。

在Java应用程序中，如果我将ImageIO.write函数指向

新文件（"/dir/test.jpg"）

我收到了一张合适的工作jpg。

这让我认为问题不在于jpg"页眉"，而在于其他地方。

谢谢你的帮助！

**编辑#1**将接收（cpp）更改为以下代码：

do {
     rbytes = recv(sockfd, ssByte, sizeof(ssByte), 0);
     if ( rbytes > 0 )
         printf("Bytes received: %dn", rbytes);
     else if ( rbytes == 0 )
         printf("Connection closedn");
     else
         printf("recv failedn");
} while( rbytes > 0 );

我看到的是，每个传入消息的最大值是8字节（最后一个是3字节）。我将尝试组合这些输入，看看它们是否建立了一个正常工作的JPG，问题是我是否可以强制Java以更大的数据包大小发送，尤其是因为这是通过localhost而不是NIC发送的。

**编辑2-替代解决方案**

除了Alnitak的解决方案，您还可以做：

这将把整个流保存到字节数组中，然后转储到文件中（以防在保存之前需要进行进一步的操作）。

unsigned char ssByte[atoi(rbuff)];
int last = 0;
if ( rbytes > 0 ) { // rbytes is from the last call, to make sure socket still open and the image isn't zero size
        do {
             rbytes = recv(sockfd, &ssByte[last], 4096, 0);
             if ( rbytes > 0 ){
                //printf("Bytes received: %dn", rbytes);
                last += rbytes;
             }
             else if ( rbytes == 0 )
                 printf("Connection closedn");
             else
                 printf("recv failedn");
        } while( rbytes > 0 );
        printf("Image: %dn", last);
        FILE *fp=fopen("/home/chen/Pictures/recv.jpg","w");
        fwrite(ssByte,sizeof(unsigned char),last, fp);
        fclose(fp);
}
return 0;

感谢所有的帮助！