Error with Request when using no Proxy

Question

I've got a problem with my VB.Net-application. When i'm trying to send a request to http://ask.fm without proxy, i got the following response in fiddler: HTTP/1.1 502 Fiddler - DNS Lookup Failed

What does this mean? And why is there no error when using a proxy server for the request?

I send the request with the following code:

  Public Function GetRequest(ByVal url As String, ByVal referer As String, ByVal cookie As CookieContainer, Optional proxy As String = "") As String

    Dim request As HttpWebRequest
    Dim response As HttpWebResponse

    Try
        Dim cookies As String = ""
        request = CType(HttpWebRequest.Create(url), HttpWebRequest)
        request.CookieContainer = cookie
        request.ServicePoint.Expect100Continue = False
        request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; rv:8.0) Gecko/20100101 Firefox/8.0"
        If referer <> "" Then
            request.Referer = referer
        End If
        request.Timeout = 10000
        If proxy <> "" Then
            request.Proxy = New WebProxy(proxy)
        End If
        response = CType(request.GetResponse(), HttpWebResponse)

        cookies = response.GetResponseHeader("Set-Cookie")

        If url.Contains("ask.fm/") Then
            If New Regex("l=.*?; domain=ask.fm; path=/;").Match(cookies).Value = "" Then
                Return "ERROR"
            End If
        End If

        Dim source As String = New StreamReader(response.GetResponseStream()).ReadToEnd()
        If source.Contains("No robots allowed!") Then
            source = "ERROR"
        End If
        If source = "" Then
            source = "ERROR"
        End If
        Return source
    Catch ex As Exception
        Return "ERROR"
    End Try

End Function

Answer 1

Are you using Fiddler to inspect the traffic? If so, make sure Fiddler can redirect your traffic correctly.

Go to Help > About Fiddler and make sure your Gateway is correct (either set to the proxy you use for accessing internet or equal to No Gateway if you can access directly).