c# socket如何传输大数据

Question

我服务端通过SOCKET向客户端发送大数据（M以上的数据），数据大后，容易掉包，用多线程的话不掉包，但是速度又比较慢了。请教各位大神了！

Answer 1

<code C#>
const int blockLength=512*1024;
public void SendFile(string filePath, NetworkStream stream)     //发送文件
        {
            //传输内容
            using (FileStream fs = File.Open(filePath, FileMode.Open))
            {
                int readLength = 0;
                byte[] data = new byte[blockLength];                //发送大小
                byte[] length = new byte[8];
                BitConverter.GetBytes(new FileInfo(filePath).Length).CopyTo(length, 0);
                stream.Write(length, 0, 8);                //发送文件
                while ((readLength = fs.Read(data, 0, blockLength)) > 0)
                {
                    stream.Write(data, 0, readLength);
                }
            }        }public bool ReceiveFile(string fileName, NetworkStream stream) //接收文件
        {
            try
            {
                long count = GetSize(stream);
                if (count == 0)
                {
                    return false;
                }
                long index = 0;
                int currentBlockLength = 0;
                int receivedBytesLen = 1;
                using (FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate))
                {
                    while (receivedBytesLen > 0 && index < count)
                    {
                        byte[] clientData = new byte[blockLength];
                        receivedBytesLen = 0;                        if (blockLength < count - index)
                        {
                            currentBlockLength = blockLength;
                        }
                        else
                        {
                            currentBlockLength = (int)(count - index);
                        }
                        receivedBytesLen = stream.Read(clientData, 0, currentBlockLength);
                        fs.Write(clientData, 0, receivedBytesLen);
                        index += receivedBytesLen;
                    }
                }
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
                return false;
            }
            return true;
        }private int GetSize(NetworkStream stream) //获取文件大小
        {
            int count = 0;
            byte[] countBytes = new byte[8];
            try
            {
                if (stream.Read(countBytes, 0, 8) == 8)
                {
                    count = BitConverter.ToInt32(countBytes, 0);
                }
                else
                {
                    return 0;
                }
            }
            catch
            {
                return 0;
            }
            return count;
        }
</code>

Answer 2

为何不行？每次写入的大小最大是512KB,再大的文件也没事呀，那个GetSize函数的返回类型改成long,不会有文件比这个还大吧

Answer 3

网络传输主要耗时原因在于网络环境，弄个56k的猫1MB你也要传个几分钟。
600Gb光纤1G也要不了一分钟。

Answer 4

不是协议的问题,应该是代码处理上! 以下为微软发送文件 sendfile函数源码!
// System.Net.Sockets.Socket
public void SendFile(string fileName, byte[] preBuffer, byte[] postBuffer, TransmitFileOptions flags)
{
if (Socket.s_LoggingEnabled)
{
Logging.Enter(Logging.Sockets, this, "SendFile", "");
}
if (this.CleanedUp)
{
throw new ObjectDisposedException(base.GetType().FullName);
}
if (!ComNetOS.IsWinNt)
{
throw new PlatformNotSupportedException(SR.GetString("WinNTRequired"));
}
if (!this.Connected)
{
throw new NotSupportedException(SR.GetString("net_notconnected"));
}
this.ValidateBlockingMode();
TransmitFileOverlappedAsyncResult transmitFileOverlappedAsyncResult = new TransmitFileOverlappedAsyncResult(this);
FileStream fileStream = null;
if (fileName != null && fileName.Length > 0)
{
fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read);
}
SafeHandle safeHandle = null;
if (fileStream != null)
{
ExceptionHelper.UnmanagedPermission.Assert();
try
{
safeHandle = fileStream.SafeFileHandle;
}
finally
{
CodeAccessPermission.RevertAssert();
}
}
SocketError socketError = SocketError.Success;
try
{
transmitFileOverlappedAsyncResult.SetUnmanagedStructures(preBuffer, postBuffer, fileStream, TransmitFileOptions.UseDefaultWorkerThread, true);
if ((safeHandle != null) ? (!UnsafeNclNativeMethods.OSSOCK.TransmitFile_Blocking(this.m_Handle.DangerousGetHandle(), safeHandle, 0, 0, SafeNativeOverlapped.Zero, transmitFileOverlappedAsyncResult.TransmitFileBuffers, flags)) : (!UnsafeNclNativeMethods.OSSOCK.TransmitFile_Blocking2(this.m_Handle.DangerousGetHandle(), IntPtr.Zero, 0, 0, SafeNativeOverlapped.Zero, transmitFileOverlappedAsyncResult.TransmitFileBuffers, flags)))
{
socketError = (SocketError)Marshal.GetLastWin32Error();
}
}
finally
{
transmitFileOverlappedAsyncResult.SyncReleaseUnmanagedStructures();
}
if (socketError != SocketError.Success)
{
SocketException ex = new SocketException(socketError);
this.UpdateStatusAfterSocketError(ex);
if (Socket.s_LoggingEnabled)
{
Logging.Exception(Logging.Sockets, this, "SendFile", ex);
}
throw ex;
}
if ((transmitFileOverlappedAsyncResult.Flags & (TransmitFileOptions.Disconnect | TransmitFileOptions.ReuseSocket)) != TransmitFileOptions.UseDefaultWorkerThread)
{
this.SetToDisconnected();
this.m_RemoteEndPoint = null;
}
if (Socket.s_LoggingEnabled)
{
Logging.Exit(Logging.Sockets, this, "SendFile", socketError);
}
}