Error while uploading large file via FTP

Question

I am trying to upload a 4 GB zip file via below code.

The same code is working for a smaller files, but it is not working with a large file. I think the exception is generated while closing the FileStream.

I am getting this error:

Message:The underlying connection was closed: An unexpected error occurred on a receive. Stacktrace: at System.Net.FtpWebRequest.SyncRequestCallback(Object obj) at System.Net.FtpWebRequest.RequestCallback(Object obj) at System.Net.CommandStream.Dispose(Boolean disposing) at System.IO.Stream.Close() at System.IO.Stream.Dispose() at System.Net.ConnectionPool.Destroy(PooledStream pooledStream) at System.Net.ConnectionPool.PutConnection(PooledStream pooledStream, Object owningObject, Int32 creationTimeout, Boolean canReuse) at System.Net.FtpWebRequest.FinishRequestStage(RequestStage stage) at System.Net.FtpWebRequest.SyncRequestCallback(Object obj) at System.Net.FtpWebRequest.RequestCallback(Object obj) at System.Net.CommandStream.Abort(Exception e) at System.Net.CommandStream.CheckContinuePipeline() at System.Net.FtpWebRequest.DataStreamClosed(CloseExState closeState) at System.Net.FtpDataStream.System.Net.ICloseEx.CloseEx(CloseExState closeState) at System.Net.FtpDataStream.Dispose(Boolean disposing) at System.IO.Stream.Close() at System.IO.Stream.Dispose() at BackupUtility.Program.UploadFileToFTP(String source)

My FTP code is:

private static bool UploadFileToFTP(string source)
{
    try
    {
        String sourcefilepath = source; // e.g. "d:/test.docx"
        String ftpurl = "myftpurl";

        String ftpusername = "ftpusername"; // e.g. username
        String ftppassword = "ftppassword"; // e.g. password

        string ftpfullpath = "mylocalftpFilePath";

        Console.WriteLine("Before Request. ftpfullpath:" + ftpfullpath);
        //  Console.ReadLine();

        FtpWebRequest ftp = (FtpWebRequest)FtpWebRequest.Create(ftpfullpath);
        ftp.Credentials = new NetworkCredential(ftpusername, ftppassword);

        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

        ftp.KeepAlive = true;
        ftp.UseBinary = true;
        ftp.Timeout = 6000000;

        ftp.Method = WebRequestMethods.Ftp.UploadFile;

        FileStream fs = File.OpenRead(source);

        byte[] buffer = new byte[8192];
        using (Stream ftpstream = ftp.GetRequestStream())
        {
            //Stream ftpstream = ftp.GetRequestStream();
            int read = 0;
            while ((read = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                ftpstream.Write(buffer, 0, read);
            }
            ftpstream.Flush();
        }

        fs.Read(buffer, 0, buffer.Length);
        fs.Close();
    }
    catch (Exception ex)
    {
        return false;
    }
    return true;
}