The remote server returned an error: (501) Syntax error in parameters or arguments.

   at System.Net.FtpWebRequest.SyncRequestCallback(Object obj)

   at System.Net.CommandStream.Dispose(Boolean disposing)

   at System.IO.Stream.Close()

   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.GetResponse()

   at EdiTranslatorTest.frmMain.DownloadFtpByWebRequest() in E:\Work\Development\DOTNET\EDI Hub\Code_NH\EdiTranslatorTest\frmMain.cs:line 187

   at EdiTranslatorTest.frmMain.btnTest_Click(Object sender, EventArgs e) in E:\Work\Development\DOTNET\EDI Hub\Code_NH\EdiTranslatorTest\frmMain.cs:line 40

System.Net Information: 0 : [7956] FtpControlStream#61476884 - Sending command [RETR Inbox/csv/serials_incremental_27_04_2017 11_43_31.csv]

Uri ftpUri = new Uri("ftp://FTPuser@xxx.xx.xxx.xx/Inbox/csv/serials_incremental_27_04_2017 11_43_31.csv");
 
FtpWebRequest ftpRequest = (FtpWebRequest)WebRequest.Create(ftpUri);
FtpWebResponse ftpResponse = null;
FileStream ftpfile = new FileStream("e:\\temp\\FTP\\serials_incremental_27_04_2017 11_43_31.csv", FileMode.Create);
ftpRequest.Credentials = new NetworkCredential("FTPuser", "Password");
ftpRequest.Method = WebRequestMethods.Ftp.DownloadFile;
ftpRequest.UseBinary = true;
ftpResponse = (FtpWebResponse)ftpRequest.GetResponse();
Stream ftpstream = ftpResponse.GetResponseStream();
 
byte[] ftpbyte = new byte[2048];
int readcout = 0;
readcout = ftpstream.Read(ftpbyte, 0, 2048);
while (readcout > 0)
{
    ftpfile.Write(ftpbyte, 0, readcout);
    readcout = ftpstream.Read(ftpbyte, 0, 2048);
}
 
ftpfile.Close();
ftpResponse.Close();
ftpstream.Close();

// Setup session options
SessionOptions sessionOptions = new SessionOptions
{
    HostName = "xxx.xx.xxx.xx",
    UserName = "FTPUser",
    Password = "Password",
    PortNumber = 21,
    Protocol = Protocol.Ftp
};
 
using (Session session = new Session())
{
    try
    {
        // Connect
        session.SessionLogPath = "e:\\temp\\ftp.log";
        session.Open(sessionOptions);
        
        var remoteFileInfos = session.EnumerateRemoteFiles("/Inbox/csv", "*.csv", EnumerationOptions.None)
            .Where(file => !file.IsDirectory)
                .OrderByDescending(file => file.LastWriteTime);
        foreach (var remoteFileInfo in remoteFileInfos)
        {
            var remoteFile = session.EscapeFileMask(String.Format("{0}", remoteFileInfo.FullName));
            var localFile = Path.GetFullPath(String.Format("e:\\temp\\{0}", remoteFileInfo.Name));
            if (!remoteFileInfo.Name.IsNullOrEmpty())
            {
                session.GetFiles(remoteFile, localFile,false).Check();
                var archiveFilePath = session.EscapeFileMask("/Inbox/Backup" + "/" + remoteFileInfo.Name);
                if (session.FileExists(archiveFilePath))
                    session.RemoveFiles(archiveFilePath);
                session.MoveFile(remoteFile, archiveFilePath);
            }
        }
        session.Close();
    }
    catch (Exception ex)
    {
        session.Dispose();//Release session
        txtOutput.Text = $"{ex.Message}\r\n{ex.StackTrace}";
    }
    // Download the selected file
}