c# - 通过套接字发送数据不完整

Question

对于我的项目，我试图在客户端中截取屏幕截图并将其通过套接字发送到服务器。我使用了一个循环来截取屏幕截图，直到手动停止为止。但是，尽管截取屏幕截图很好，但是在发送一些图像后，它仅占主图像的一半，而某些图像已满。
客户:
我正在与此截图

bmpScreenshot = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);
gfxScreenshot = Graphics.FromImage(bmpScreenshot);
gfxScreenshot.CopyFromScreen(Screen.PrimaryScreen.Bounds.X, Screen.PrimaryScreen.Bounds.Y, 0, 0, Screen.PrimaryScreen.Bounds.Size, CopyPixelOperation.SourceCopy);
bmpScreenshot.Save(path + i + ".png");
ClientService.SendFile(path + i + ".png");
i++;

和SendFile方法是

public static void SendFile(string fileName)
        {
            try
            {
                IPAddress[] ipAddress = Dns.GetHostAddresses("localhost");
                IPEndPoint ipEnd = new IPEndPoint(ipAddress[0], 5656);
                Socket clientSock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);

                string filePath = "";

                fileName = fileName.Replace("\\", "/");
                while (fileName.IndexOf("/") > -1)
                {
                    filePath += fileName.Substring(0, fileName.IndexOf("/") + 1);
                    fileName = fileName.Substring(fileName.IndexOf("/") + 1);
                }

                byte[] fileNameByte = Encoding.ASCII.GetBytes(fileName);
                if (fileNameByte.Length > 600 * 1024)
                {
                    showMsg = "File size is more than 600kb, please try with small file.";
                    return;
                }

                byte[] fileData = File.ReadAllBytes(filePath + fileName);
                byte[] clientData = new byte[4 + fileNameByte.Length + fileData.Length];
                byte[] fileNameLen = BitConverter.GetBytes(fileNameByte.Length);

                fileNameLen.CopyTo(clientData, 0);
                fileNameByte.CopyTo(clientData, 4);
                fileData.CopyTo(clientData, 4 + fileNameByte.Length);

                clientSock.Connect(ipEnd);
                clientSock.Send(clientData);
                clientSock.Close();

            }
            catch (Exception ex)
            {
                if (ex.Message == "No connection could be made because the target machine actively refused it")
                    showMsg = "File Sending fail. Because server is not running.";
                else
                    showMsg = "File Sending fail." + ex.Message;
            }
        }

服务器

IPEndPoint ipEnd;
    Socket sock;
    public ServerService()
    {
        ipEnd = new IPEndPoint(IPAddress.Any, 5656);
        sock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
        sock.Bind(ipEnd);
    }

    public static string receivedPath;
    internal void StartServer()
    {
        try
        {
            sock.Listen(100);

            Socket clientSock = sock.Accept();

            byte[] clientData = new byte[1024 * 5000];

            int receivedBytesLen = clientSock.Receive(clientData);

            int fileNameLen = BitConverter.ToInt32(clientData, 0);
            string fileName = Encoding.ASCII.GetString(clientData, 4, fileNameLen);

            BinaryWriter bWrite = new BinaryWriter(File.Open(receivedPath + "/" + fileName, FileMode.Append)); ;
            bWrite.Write(clientData, 4 + fileNameLen, receivedBytesLen - 4 - fileNameLen);

            bWrite.Close();
            clientSock.Close();
        }
        catch (Exception ex)
        {
            ShowMsg = "Something is wrong." + ex.Message;
        }
    }

我怎么解决这个问题？

Answer 1

Receive仅保证用于(其中之一):

返回至少1个字节

表示EOF(非正字节)

指示错误

仅仅调用 Receive是不够的。您需要循环调用它，直到:

您已经阅读了所有想要的数据

您将获得一个EOF

您收到错误

对于您的情况，我建议您要:

精确读取4个字节(可能需要循环)以获取名称长度n

然后精确地读取n字节以读取名称

然后读取，直到获得EOF(Receive的非肯定结果)

另外:您可能想使用基于 Stream的API进行文件访问(读取和写入)，而不是 File.ReadAllBytes或 BinaryWriter。

精确读取 n字节是一种类似情况:

public void ReceiveExactly(Socket socket, byte[] buffer, int offset, int count)
{
    int read;
    while(count > 0 && (read = socket.Receive(buffer, offset, count,
        SocketFlags.None)) > 0)
    {
        offset += read;
        count -= read;
    }
    if(count != 0) throw new EndOfStreamException();
}