使用套接字（C＃）進行文件傳輸-接收的文件不包含完整數據

Question

我創建了一個服務器和一個客戶端，用於使用套接字連接進行文件傳輸。 我面臨的問題是，如果接收的文件大小超過8KB，則文件不完整。

如果您遇到此問題，可以指導我找出問題所在（在服務器/客戶端）嗎？

這是兩種方法：

客戶：

#region FILE TRANSFER USING C#.NET SOCKET - CLIENT

class FTClient
{
    public static string curMsg_client = "Idle";
    public static void SendFile(string fileName)
    {
        try
        {
            //IPAddress[] ipAddress = Dns.GetHostAddresses("localhost");
            //IPEndPoint ipEnd = new IPEndPoint(ipAddress[0], 5656);

            string IpAddressString = "192.168.1.102";
            IPEndPoint ipEnd_client = new IPEndPoint(IPAddress.Parse(IpAddressString), 5656);
            Socket clientSock_client = 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.UTF8.GetBytes(fileName);
            if (fileNameByte.Length > 5000 * 1024)
            {
                curMsg_client = "File size is more than 5Mb, please try with small file.";
                return;
            }

            curMsg_client = "Buffering ...";
            string fullPath = filePath + fileName;

            byte[] fileData = File.ReadAllBytes(fullPath);
            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);

            curMsg_client = "Connection to server ...";
            clientSock_client.Connect(ipEnd_client);

            curMsg_client = "File sending...";
            clientSock_client.Send(clientData, 0, clientData.Length, 0);

            curMsg_client = "Disconnecting...";
            clientSock_client.Close();
            curMsg_client = "File [" + fullPath + "] transferred.";

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

    }
}

#endregion

和服務器：

#region FILE TRANSFER USING C#.NET SOCKET - SERVER

class FTServer
{
    IPEndPoint ipEnd_server;
    Socket sock_server;
    public FTServer()
    {
        //make IP end point to accept any IP address with port 5656
        //these values will be altered depending on ******* (and/or other ImportSystem)
        //this was initially coded, but threw a SocketException on sock.Bind(ipEnd) {Only one usage of each socket address (protocol/network addres/port) is normally permitted}
        //ipEnd = new IPEndPoint(IPAddress.Any, 5656);
        //
        //I'll set it like this (giving the IP through a string)
        string IpAddressString = "192.168.1.102";
        ipEnd_server = new IPEndPoint(IPAddress.Parse(IpAddressString), 5656);
        //
        //creating new socket object with protocol type and transfer data type
        sock_server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
        //bind end point with newly created socket
        sock_server.Bind(ipEnd_server);
    }
    public static string receivedPath = @"C:\Users\Adrian.Constantin\Desktop\Simulare_Forder_Import\";
    public static string curMsg_server = "Stopped!";


    public void StartServer()
    {
        try
        {
            curMsg_server = "Starting...";

            sock_server.Listen(100);

            curMsg_server = "Running and waiting to receive file.";

            Socket clientSock = sock_server.Accept();

            byte[] clientData = new byte[512000];

            int receivedBytesLen = clientSock.Receive(clientData, SocketFlags.None);
            clientSock.ReceiveBufferSize = 8192;

            curMsg_server = "Receiving data...";

            int fileNameLen = BitConverter.ToInt32(clientData, 0);
            string fileName = Encoding.UTF8.GetString(clientData, 4, fileNameLen);

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

            curMsg_server = "Saving file...";
            bWrite.Close();

            clientSock.Close();
            curMsg_server = "Received and Archived file [" + fileName + "]; Server stopped.";

        }
        catch (SocketException ex)
        {
            curMsg_server = "File Receving error.";
            MessageBox.Show(String.Format("{0} Error cide: {1}", ex.Message, ex.ErrorCode));
        }
    }


}

#endregion

編輯：24.08.2012（我設法找出問題並使服務器正常工作）服務器的完整代碼是： 服務器：

#region FILE TRANSFER USING C#.NET SOCKET - SERVER

class FTServer
{
    IPEndPoint ipEnd_server;
    Socket sock_server;
    public FTServer()
    {
        string IpAddressString = "192.168.1.102";
        ipEnd_server = new IPEndPoint(IPAddress.Parse(IpAddressString), 5656);
        sock_server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP);
        sock_server.Bind(ipEnd_server);
    }
    public static string receivedPath = @"C:\";
    public static string curMsg_server = "Stopped!";


    public void StartServer()
    {
        try
        {
            curMsg_server = "Starting...";

            sock_server.Listen(100);

            curMsg_server = "Running and waiting to receive file.";

            Socket clientSock = sock_server.Accept();
            clientSock.ReceiveBufferSize = 16384;

            byte[] clientData = new byte[1024 * 50000];

            int receivedBytesLen = clientSock.Receive(clientData, clientData.Length, 0);
            curMsg_server = "Receiving data...";

            int fileNameLen = BitConverter.ToInt32(clientData, 0);
            string fileName = Encoding.UTF8.GetString(clientData, 4, fileNameLen);

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


            while (receivedBytesLen > 0)
            {
                receivedBytesLen = clientSock.Receive(clientData, clientData.Length, 0);
                if (receivedBytesLen == 0)
                {
                    bWrite.Close();
                }
                else
                {
                    bWrite.Write(clientData, 0, receivedBytesLen);
                                        }
            }


            curMsg_server = "Saving file...";
            bWrite.Close();

            clientSock.Close();
            curMsg_server = "Received and Archived file [" + fileName + "] (" + (receivedBytesLen - 4 - fileNameLen) + " bytes received); Server stopped.";

        }
        catch (SocketException ex)
        {
            curMsg_server = "File Receving error.";
            MessageBox.Show(String.Format("{0} Error code: {1}", ex.Message, ex.ErrorCode));
        }
    }

}

#endregion

Answer 1

您已陷入套接字使用的最經典陷阱。 這與Berkely開發的插座的想法一樣古老。

你看，你還沒有看過文檔:)

例如，請參見http://msdn.microsoft.com/zh-cn/library/ms145160.aspx-返回值是多少？

Send和Receive方法都沒有義務實際發送/接收您提供的所有數據。 這就是為什么它們都返回一個“ int”來描述實際發送/接收的數量的原因。 之所以保留這種設計，是因為系統的內部緩沖區受到限制。 如果您提供要發送的999GB陣列，那么網卡在實際發送之前將如何存儲？

您會看到8KB閾值的行為，可能是因為這是內部緩沖區的大小，或者可能是TCP網絡數據包的最大大小。。我不記得它們有多大，但是大約是這樣。

要流行地發送和接收數據，您必須使用某種循環，例如以簡單形式：

int bytesToBeSent = arr.Length;
int bytesActuallySent = 0;
while(bytesActuallySent < bytesToBeSent)
    bytesActuallySent += socket.Send(arr, bytesActuallySent, bytesToSend - bytesActuallySent, ....);

和recv-類似。

Answer 2

從MSDN ：

Receive方法將讀取盡可能多的數據，最多可達size參數指定的字節數

它不能*保證一口氣閱讀所有內容； 它讀取它可以達到最大（緩沖區你的情況的大小）。 從任何流中讀取數據時，通常都需要具有“讀取/接收”循環。 在您的情況下，我會說緩沖區很大，您應該手動讀取長度字節，然后在較小的緩沖區（例如4096字節）上進行讀/接收循環以進行文件處理。 您不需要512k緩沖區。

經典的讀取/接收循環為：

int read;
byte[] buffer = new byte[4096];
while((read = socket.Receive(buffer)) > 0) {
    output.Write(buffer, 0, read);
}

Answer 3

在每種發送方法之前，您都需要大約200毫秒的延遲，因為接收緩沖區會被傳入數據覆蓋。 例：

Thread.Sleep(200);
socket.send(sendbuffer);