Best method to close a keep-alive FTP or FTPS conn

问题:

In C# (.NET 4.6) I am using a keep-alive FTPS connection to download a couple of files in a loop like this:

foreach (string filename in filenames)
{
  string requestUriString = GetFtpUriString(myDir) + "/" + filename;
  FtpWebRequest request = (FtpWebRequest)WebRequest.Create(requestUriString);
  request.Method = WebRequestMethods.Ftp.DownloadFile;
  request.Credentials = new NetworkCredential(myFtpsUsername, myFtpsPassword);
  request.EnableSsl = true;
  request.ConnectionGroupName = myConnectionGroupName;
  request.KeepAlive = true;

  ... do something ...
}

After the loop is done, I want to close the connection. I could not find a direct way to accomplish this. What I came up with is the following work-around, which makes another low-footprint request to the FTP server, this time with the KeepAlive flag set to false:

FtpWebRequest request = (FtpWebRequest)WebRequest.Create(GetFtpUriString(myDir));
request.Method = WebRequestMethods.Ftp.PrintWorkingDirectory;
request.Credentials = new NetworkCredential(myFtpsUsername, myFtpsPassword);
request.EnableSsl = true;
request.ConnectionGroupName = myConnectionGroupName;
request.KeepAlive = false;
FtpWebResponse response = (FtpWebResponse)request.GetResponse();
response.Close();

I am wondering now whether there exists another, simpler, more elegant and direct way to close an open FTP connection for a specific connection group.

回答1:

The connection pool of FtpWebRequest instances does not have any public interface.

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But there's an easy solution, just set the KeepAlive to false in the last round of the loop.