Ftpwebrequest - Error large files

Question

I have a c# desktop application running a few months on a client. The same requested a module to perform uploads and downloads on an FTP server, the database is currently in the clouds by Kinghost, as this company already offers the service, I chose to continue in it, but I’m having some problems...

My algorithm does not present any problem to upload small files, however more than 20MB files is occurring the following error: "The underlying connection was closed: Unexpected error on a receipt"

I contacted the hosting company and was informed that no problem was located.

DETAIL: after few minutes of error, while checking the ftp the file is there...

Follows algorithm:

                    FtpWebRequest request = (FtpWebRequest)FtpWebRequest.Create(cboServidor.Text + cboGrupoArquivo.Text + "/" + Path.GetFileName(openFileDialog1.FileName));
                    request.Method = WebRequestMethods.Ftp.UploadFile;
                    request.Credentials = new NetworkCredential(txtUsuario.Text, txtSenha.Text);
                    request.UsePassive = true;
                    request.UseBinary = true;
                    request.KeepAlive = false;


                    FileStream stream = File.OpenRead(openFileDialog1.FileName);
                    byte[] buffer = new byte[stream.Length];

                    stream.Read(buffer, 0, buffer.Length);
                    stream.Close();

                    Stream reqStream = request.GetRequestStream();
                    reqStream.Write(buffer, 0, buffer.Length);
                    reqStream.Close();