FTP Problem

[simonm]

I seem to be having a problem with the FTPWebRequest. I get an error (see below code) when it executes the emboldened line. Any ideas?

Dim uploadRequest As FtpWebRequest = WebRequest.Create(uploadUrl)
uploadRequest.Method = WebRequestMethods.Ftp.UploadFile

If strUserName <> "" And strPassword <> "" Then
       uploadRequest.Credentials = New System.Net.NetworkCredential(strUserName, strPassword)
End If

uploadRequest.EnableSsl = blnSecure
uploadRequest.KeepAlive = True
uploadRequest.UsePassive = blnPassive
uploadRequest.Proxy = Nothing

RequestStream = uploadRequest.GetRequestStream()
fileStream = File.Open(fileName, FileMode.Open)

Dim buffer(1024) As Byte
Dim bytesRead As Integer
While True
        bytesRead = fileStream.Read(buffer, 0, buffer.Length)
        If bytesRead = 0 Then
            Exit While
        End If
        requestStream.Write(buffer, 0, bytesRead)
End While

' The request stream must be closed before getting the response.
requestStream.Close()

uploadResponse = uploadRequest.GetResponse()

"The server returned an address in response to the PASV command that is different than the address to which the FTP connection was made."

[Jenner]

Ugh, never seen that one. Is this in a test-bed situation or live? Do you know your network route to the server? Are there anything like proxy servers, firewalls or anything else in between that could be passing you a different IP?

[mendhak]

Is the server you're talking to on multiple IP addresses? Try accessing it by IP address rather than relying on DNS resolutions.

[simonm]

In answer to the above questions:

I am accessing it with an IP address rather than a DNS.
This is a testbed situation.
there are no proxy servers but there is a firewall.

I should have stated originally that this problem occurs when I am setting EnableSsl to True. I am also using passive mode (because I heard somewhere that you have to when using encryption). If I set EnableSsl to False, it uploads fine.

Further note, I have connected to the FTP server in question fine using a client tool (such as SmartFTP) with Explicit SSL and Passive mode switched on. The client tool works but the .NET code doesn't...