Hello folks,

I'm having a problem uploading files.  The code that is responsible for this
works almost all the time, but fails when trying to upload files that
approach a megabyte in size or more, from a server that has a slow internet
connection.  The exceptions I get are:

System.Net.WebException: The underlying connection was closed: The request
was canceled.
  at System.Net.HttpWebRequest.GetResponse()

System.Net.WebException: The operation has timed-out.
  at System.Net.HttpWebRequest.GetResponse()

Some pertinent facts:
- I also get this error when using WebClient.UploadFile.
- Both servers are using the 1.1 version of the .net framework.  
- The sender is running windows server 2003.
- The receiver is running windows 2000 server.
- Uses https.
- No anonymous access, basic & integrated windows authentication.
- The receiving aspx page is never executed.
- The weblogs for the failed cases show a hit without credentials resulting
in a 401, followed just less than 2 minutes later with a hit without
credentials resulting in a 500.
- Good credentials are being supplied ( the code works for smaller files, &
faster connections ).
- Specifying SendChunked does not affect the outcome.

The code in question:

//----------
NetworkCredential cred = new NetworkCredential( sUser, sPassword, sDomain );
Uri uri = new Uri( sURL );
HttpWebRequest req = ( HttpWebRequest )WebRequest.Create( uri );

req.Credentials = cred;
req.ContentType = "multipart/form-data; boundary=" + sBoundary;
req.Method = "POST";

using ( FileStream stmFile = new FileStream( sFileName, FileMode.Open,
FileAccess.Read ) ) {
    long lContentLength = bufPostHeader.Length + stmFile.Length +
bufBoundary.Length;

    req.ContentLength = lContentLength;

    using ( Stream stmReq = req.GetRequestStream() ) {
        //    Write out our post header
        stmReq.Write( bufPostHeader, 0, bufPostHeader.Length );

        //    Write out the file contents
        byte[] buf = new Byte[ 4096 ];
        int iBytesRead = 0;
        while ( ( iBytesRead = stmFile.Read( buf, 0, buf.Length ) ) != 0 ) {
            stmReq.Write( buf, 0, iBytesRead );
        }

        //    Write out the trailing boundary
        stmReq.Write( bufBoundary, 0, bufBoundary.Length );
    }
}

string sRsp;
using ( WebResponse rsp = req.GetResponse() ) {
    using ( Stream stmRsp = rsp.GetResponseStream() ) {
        StreamReader sr = new StreamReader( stmRsp );
        sRsp = sr.ReadToEnd();
    }
}
//----------

This problem has me stumped.  I guess my next option is to use the
asynchronous calls & implement my own timeout mechanism, but I was really
hoping that someone, somewhere had encountered this issue & could point me to
a solution so I don't have to continue sinking time coding in the dark.

Thanks for any help....