FtpWebRequest use STOU mode can not upload

Question

I use FtpWebRequest to upload a file to FTP, if I set the method to WebRequestMethods.Ftp.UploadFileWithUniqueName, following exception will be catched in line

Stream requestStream = request.GetRequestStream();

System.Net.WebException: 'The remote server returned an error: (550) File unavailable (e.g., file not found, no access).'

This is my source code. And the .NET Framework is .NET Framework 4

FtpWebRequest request;

                string absoluteFileName = Path.GetFileName(fileName);

                request = WebRequest.Create(new Uri(string.Format(@"ftp://{0}/{1}", fullAddr, absoluteFileName))) as FtpWebRequest;
                request.Method = WebRequestMethods.Ftp.UploadFileWithUniqueName;
                request.UseBinary = true;
                request.KeepAlive = false;
                request.UsePassive = false;
                request.Credentials = new NetworkCredential(user, pass);
                request.Proxy = null;                

                using (FileStream fs = File.OpenRead(fileName))
                {
                    request.ContentLength = fs.Length;
                    byte[] buffer = new byte[fs.Length];
                    fs.Read(buffer, 0, buffer.Length);
                    fs.Close();
                    fs.Dispose();
                    Stream requestStream = request.GetRequestStream();
                    requestStream.Write(buffer, 0, buffer.Length);
                    requestStream.Flush();
                    requestStream.Close();
                }

Answer 1

Hi, welcome to Microsoft Q&A.

Check if the policy for the target FTP service is set to read-only?

When the destination file already exists, STOU creates a new file with a unique file name to store the uploaded file.

Best Regards. 

Jiachen Li 

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