Asp – Is the ftp issue a coding error or credentials error

asp.netftp

I am using ASP.NET 2.0 and I am trying, for the first time, to ftp a file through the app. There are several examples on the net. This one made the most sense to me. Being unsure of the actual local it will be going, right now, I decided to FTP it right back to my local host, figuring I have the credential so it would be a good test. However, it is failing with the following error: "Unable to connect to the remote server".

public void FTPFile()
        {
            string CompleteFTPPath = "ftp://localhost//WebSite1/test.txt";
            string CompleteLocalPath = "C:\\test_file.txt";

        //Create a FTP Request Object and Specfiy a Complete Path 
        FtpWebRequest reqObj = (FtpWebRequest)WebRequest.Create(CompleteFTPPath);

        reqObj.Method = WebRequestMethods.Ftp.UploadFile;

        reqObj.Credentials = new NetworkCredential("<my user name>", "<my pw>");

        FileStream streamObj = File.OpenRead(CompleteLocalPath);

        byte[] buffer = new byte[streamObj.Length];

        streamObj.Read(buffer, 0, buffer.Length);

        streamObj.Close();
        streamObj = null;

        reqObj.GetRequestStream().Write(buffer, 0, buffer.Length);

        reqObj = null;
    }

Best Solution

Make sure the ftp server is listening on the localhost (127.0.0.1) and not just on it's network ip address.

Related Solutions

Asp – AsyncCallback in .net web page run away

I'm guesing your top chunk of code is in the Page_Load handler? And the line

 ftp.Upload(fn);

Is causing the problem? If so I'd say your users were reloading the page, so this is getting called much more often than before.

You are on the right lines to look at async patterns, but it sound like you need to guard against the case where people refresh the page too much.

The difference between active and passive FTP

Active and passive are the two modes that FTP can run in.

For background, FTP actually uses two channels between client and server, the command and data channels, which are actually separate TCP connections.

The command channel is for commands and responses while the data channel is for actually transferring files.

This separation of command information and data into separate channels a nifty way of being able to send commands to the server without having to wait for the current data transfer to finish. As per the RFC, this is only mandated for a subset of commands, such as quitting, aborting the current transfer, and getting the status.

In active mode, the client establishes the command channel but the server is responsible for establishing the data channel. This can actually be a problem if, for example, the client machine is protected by firewalls and will not allow unauthorised session requests from external parties.

In passive mode, the client establishes both channels. We already know it establishes the command channel in active mode and it does the same here.

However, it then requests the server (on the command channel) to start listening on a port (at the servers discretion) rather than trying to establish a connection back to the client.

As part of this, the server also returns to the client the port number it has selected to listen on, so that the client knows how to connect to it.

Once the client knows that, it can then successfully create the data channel and continue.

More details are available in the RFC: https://www.ietf.org/rfc/rfc959.txt

Related Question