Why Ftp Downloading is so slow with c# / FtpWebRequest

Question

I'm using the FTP function in c# in order to download somes files. My problem is that the download is slow.

I don't have any problem with Filezilla, and my connection is OK.

I'm thinking about the FTP functions implementations, here is my code :

    public static string DownloadFromList(string strParam,string filePath)
    {
        string[] FilesToDownload = strParam.Split('\n');

        try
        {
            FtpWebRequest reqFTP;

            foreach(string file in FilesToDownload)
            {
                string tmpfile = file;

                if (tmpfile.Contains("\n"))
                {
                    tmpfile = tmpfile.Replace('\n', ' ');
                }
                FileInfo fileToDownload = new FileInfo(tmpfile);
                tmpfile = fileToDownload.Name;

                FileStream outputStream = new FileStream(filePath.Trim() + "\\" + tmpfile.Trim(), FileMode.Create);

                if (strDirectory.Trim() != "")
                {
                    reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + strHost.Trim() + "/" + strDirectory.Trim() + "/" + tmpfile.Trim()));
                }
                else
                {
                    reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + strHost.Trim() + "/" + tmpfile.Trim()));
                }

                reqFTP.ConnectionGroupName = "MyGroupName"; 

                reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
                reqFTP.UseBinary = true;
                reqFTP.KeepAlive = true;
                reqFTP.Timeout = -1;
                reqFTP.Credentials = new NetworkCredential(strUser.Trim(), strPass.Trim());
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                Stream ftpStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(ftpStream, System.Text.Encoding.UTF8);
                long cl = response.ContentLength;
                int bufferSize = 8192;
                char[] bytesInStream = new char[8192];
                int readCount;

                StreamWriter sw = new StreamWriter(outputStream);
                int len;
                while ((len = reader.Read(bytesInStream, 0, bytesInStream.Length)) > 0)
                {
                    sw.Write(bytesInStream, 0, len);
                }
                sw.Close();
                outputStream.Close();
                ftpStream.Close();
                response.Close();
            }

            return "ok";
        }
        catch (Exception ex)
        {
            return (ex.Message);
        }
    }

• Is it necessary to set useBinary = true ?
• KeepAlive is setted to true in order to use the same connection, but is it true ?
• Is it possible to set the credential only one time ?

How can i improve this please?

Thanks a lot :)

Best regards,