Sending files using socket, clean buffer problem

Question

4.00/5 (1 vote)

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Dears
i have the following method that sends files using sockets

C#

public static void SendFile(string path, string fName,int nbOfFiles ,string strCommand, string strIPadd, int iPortNb,ref Socket clientSock)
{
    try
    {
        clientSock.SetSocketOption(SocketOptionLevel.Socket,SocketOptionName.SendBuffer, 0);
        byte[] clientData;
        byte[] fileName = Encoding.UTF8.GetBytes(fName); //file name
        byte[] fileData = File.ReadAllBytes(path); //file
        byte[] fileNameLen = BitConverter.GetBytes(fileName.Length); //lenght of file name
        byte[] bCommand = Encoding.UTF8.GetBytes(strCommand);// Command
        byte[] bComandLength = BitConverter.GetBytes(bCommand.Length); // length of command
        byte[] bNBofFiles = { Convert.ToByte(nbOfFiles), }; //nb of files to be sent to server

        clientData = new byte[12 + bCommand.Length + fileName.Length + fileData.Length];

        bComandLength.CopyTo(clientData, 0);
        bCommand.CopyTo(clientData, 4);
        bNBofFiles.CopyTo(clientData, 4 + bCommand.Length);
        fileNameLen.CopyTo(clientData, 8 + bCommand.Length);
        fileName.CopyTo(clientData, 12 + bCommand.Length);
        fileData.CopyTo(clientData, 12 + fileName.Length + bCommand.Length);

        clientSock.Send(clientData);
        strBuild.AppendEntry("Sending Files to Server Succeeded");

    }
    catch (Exception e)
    {
        strBuild.AppendEntry(e.Message);
    }

}

and the method for receiving is

C#

receivedBytesLen = clientSock.Receive(clientDataFiles);

int commandLength = BitConverter.ToInt32(clientDataFiles, 0); //length of command
strCommandReceived = Encoding.ASCII.GetString(clientDataFiles, 4, commandLength);//command received
iNbofFiles = BitConverter.ToInt32(clientDataFiles, 4 + commandLength);//nb of files

int fileNameLen = BitConverter.ToInt32(clientDataFiles, 8 + commandLength);
fileName = Encoding.ASCII.GetString(clientDataFiles, 12 + commandLength, fileNameLen);

strDirectory = terminal.TerminalPath + "\\" + terminal.TerminalID + "\\" + command.CommandPath;
if (!Directory.Exists(strDirectory))
    Directory.CreateDirectory(strDirectory);

if (iNbofFiles > 1)
{
    filePath = terminal.TerminalPath + "\\" + terminal.TerminalID + "\\" + command.CommandPath + "\\" + fileName;
}
else
{
    filePath = terminal.TerminalPath + "\\" + terminal.TerminalID + "\\" + command.CommandPath + "\\" + command.FileName;
}

if (!System.IO.File.Exists(filePath))
    System.IO.File.Create(filePath).Close();

BinaryWriter bWrite = new BinaryWriter(File.Open(filePath, FileMode.Create)); ;
bWrite.Write(clientDataFiles, 12 + fileNameLen + commandLength, receivedBytesLen - 12 - fileNameLen - commandLength);
bWrite.Close();

The problem "Index and count must refer to a location within the buffer" is taking place when i send more than one large files. If i send 3 small files this problem doesn't occur. Any ideas of how i can clean the buffer before sending the next file
i tried to use
clientSock.SetSocketOption(SocketOptionLevel.Socket,SocketOptionName.SendBuffer, 0);
and i used 1 instead of 0 and nothing changed

Regards,

Posted 6-Aug-12 20:39pm

Sandra Ha

Updated 7-Aug-12 2:08am

Richard MacCutchan

v2

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Comments

Richard MacCutchan 7-Aug-12 4:12am

Your question is not clear; what is the 'problem' you refer to?

Sandra Ha 7-Aug-12 6:13am

Whenever i try to send more than one file,i cannot because the buffer is full, and an exception is thrown, so what i need to do is clean the buffer before i send a new file

Richard MacCutchan 7-Aug-12 6:23am

You do not need to clean the buffer, just reset the pointers when it is full and start at the beginning again. Also if you get an exception please post the details in your question so people can help you to diagnose the problem.

Sandra Ha 7-Aug-12 7:37am

When i send a file the buffer is filled and the index of the buffer is pointed at a specific location. When i send the second file the bytes will be written starting from where the buffer index was located. Since the remaining buffer size is smaller than the second file size i am having this error
"Index and count must refer to a location within the buffer"
And what pointers i have to reset if you can specify

Richard MacCutchan 7-Aug-12 8:05am

Why not just re-use the buffer completely? When the first file has been sent, start filling the buffer from the beginning. Indeed you can dispose of the first buffer after its data has been sent and start a new one for the next file. Using the method you describe, you will obviously run out of space at some time.

Sandra Ha 7-Aug-12 8:19am

Can you specify me some syntax for reusing the buffer?

Richard MacCutchan 7-Aug-12 10:49am

You already have the syntax in your code above. Just create a new reference, like:


byte[] fileData = File.ReadAllBytes(path); //file
// or
byte[] fileData = new byte[512];

Sandra Ha 7-Aug-12 15:00pm

After debugging i found that the problem is asynchronous sending and receiving between the send and receive methods. It's not the buffer nor anything else. For example, if I'm debugging the process is slowed down so problems are more frequent to occur such as receiving incomplete file (1/2) the size of the file is received.However, if both are running with no debugging that slows down the process, the file is received completeley. I'm trying to find a solution since my major problem is sending more than one file

Richard MacCutchan 7-Aug-12 16:58pm

So you need to add some synchronisation code, and make sure that you do not overwrite any buffer until it has been transferred completely.

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Richard MacCutchan · Answer 1 · 2012-08-07T00:28:00

You should try and use a more logical approach to the transfer. Get the basic details of the file and send that to your receiving station. Then read the file data in 'blocks' and send each block in turn. The receiver should accept each block and rebuild the file by writing each block in turn. You can then repeat this process for any file, or number of files.