File Transfer

Posted on 2006-07-18
Last Modified: 2013-11-20
I am sending files from ona pda to other, i have problem in the client side, the code worked fine but after a day it is not working, i am getting an error sending the file size(Error2 in the code), can anyone tell how to solve this problem and also a better way to trouble shooting the errors.

BOOL CFinalVersionDlg::OnBreceive()

    // connects to a remote server and downloads a file from it
    // the remote server must be running a counterpart
    //    CString fName = name of local file to which
    //    downlaoded data will be stored
    // Output: BOOL return value indiactes success or failure of the download

    // create client socket and connect to server
    ///    AfxSocketInit(NULL);
    // make certain this is done somewhere in each thread
    // (usually in InitInstance for main thread)
    CSocket sockClient;

   // PRE_AGREED_PORT is #define'd as 8686
      CString strIP="";
   sockClient.Connect( strIP, PRE_AGREED_PORT );
    // local variables used in file transfer (declared here to avoid
    // "goto skips definition"-style compiler errors)
    BOOL bRet = TRUE; // return value
    // used to monitor the progress of a receive operation
    int dataLength, cbBytesRet, cbLeftToReceive;
    // pointer to buffer for receiving data
    // (memory is allocated after obtaining file size)
    BYTE* recdData = NULL;
    CFile destFile;
    CFileException fe;
    BOOL bFileIsOpen = FALSE;
    // open/create target file that receives the transferred data
    TCHAR* pathName = _T("hi.txt");
    if( !( bFileIsOpen = destFile.Open( pathName, CFile::modeCreate |
           CFile::modeWrite | CFile::typeBinary, &fe ) ) )
        TCHAR strCause[256];
        fe.GetErrorMessage( strCause, 255 );
        /* you should handle the error here */
        bRet = FALSE;
        goto PreReturnCleanup;
    // get the file's size first
    cbLeftToReceive = sizeof( dataLength );
        BYTE* bp = (BYTE*)(&dataLength) + sizeof(dataLength) - cbLeftToReceive;
        cbBytesRet = sockClient.Receive( bp, cbLeftToReceive );
        // test for errors and get out if they occurred
        if ( cbBytesRet == SOCKET_ERROR || cbBytesRet == 0 )
            int iErr = ::GetLastError();
            /* you should handle the error here */
            bRet = FALSE;
            goto PreReturnCleanup;
        // good data was retrieved, so accumulate
        // it with already-received data
        cbLeftToReceive -= cbBytesRet;
    while ( cbLeftToReceive > 0 );

    dataLength = ntohl( dataLength );

    // now get the file in RECV_BUFFER_SIZE chunks at a time
    recdData = new byte[RECV_BUFFER_SIZE];
    cbLeftToReceive = dataLength;
        int iiGet, iiRecd;

        iiGet = (cbLeftToReceive<RECV_BUFFER_SIZE) ?
                      cbLeftToReceive : RECV_BUFFER_SIZE ;
        iiRecd = sockClient.Receive( recdData, iiGet );

        // test for errors and get out if they occurred
        if ( iiRecd == SOCKET_ERROR || iiRecd == 0 )
            int iErr = ::GetLastError();
            /* you should handle the error here */
            bRet = FALSE;
            goto PreReturnCleanup;

        // good data was retrieved, so accumulate
        // it with already-received data
        destFile.Write( recdData, iiRecd); // Write it
        cbLeftToReceive -= iiRecd;

    while ( cbLeftToReceive > 0 );

      MessageBox(TEXT("File Downloaded"),MB_OK);

PreReturnCleanup: // labelled "goto" destination
    // free allocated memory
    // if we got here from a goto that skipped allocation,
    // delete of NULL pointer
    // is permissible under C++ standard and is harmless
    delete[] recdData;        
    if ( bFileIsOpen )
        // only close file if it's open (open might have failed above)
    return bRet;
Question by:Prakashv20
  • 3
LVL 22

Expert Comment

ID: 17136196
You have not initialized 'dataLength' parameter anywhere ? I can see you have directly used dataLength after declaration...also I have not seen you have retrieved File Size for destFile anywhere ???....

 // get the file's size first
    cbLeftToReceive = sizeof( dataLength ); <== ?

and File Size can be obtained using CFile::GetLength() function......

int nFileSize = destFile.GetLength(); <== this will retrieve file size for destFile and will assign to nFileSize..

LVL 22

Accepted Solution

mahesh1402 earned 250 total points
ID: 17136211
So I think if you want file size for destFile in dataLength your code should be look like :

   dataLength = destFile.GetLength()  // get the file's size first

   cbLeftToReceive = dataLength;    // Note to assign size of file which is present in dataLength to initially assign to cbLeftToReceive ( and NOT size of dataLength )

  // Proceed with file receive loop

LVL 22

Expert Comment

ID: 17158778
so prakash how you solved your problem ?

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