SMS HTTP API call from ASP.NET is slow

Question

For a web application, I am creating a SMS module that can send an SMS from the application. My SMS provider has an API that I can call over HTTP.

The API is called via an XmlTextReader who just reads the XML response from the API.

Now my problem is: When I send the SMS from a web page (basically just doing an HTTP request) it takes more than a minute before I receive the SMS.

But when I run the exact same code from a Windows console application, my SMS arrives in less then 5 seconds.

I have done multiple tests with this, and it's not really my SMS provider who is slow. Somehow, the HTTP request gets delayed from within the ASP.NET engine, and it does not delay directly from an console application. Is there a solution?

This is the way I'm calling the HTTP API:

 Dim strPostString As String = Convert.ToString(muriPostUrl) & mstrPostPath
    If mblnUseSecureConnection Then
        strPostString = Convert.ToString(muriSecurePostUrl) & mstrPostPath
    End If

    Dim strDataString As String = "username=" & mstrUsername
    strDataString += "&" & "password=" & mstrPassword
    strDataString += "&" & "originator=" & mstrOriginator
    strDataString += "&" & "recipients=" & mstrRecipients
    strDataString += "&" & "gateway=" & mstrGateway
    strDataString += "&" & "reference=" & mstrReference
    strDataString += "&" & "message=" & mstrMessage

    If mstrType <> String.Empty Then
        strDataString += "&" & "type=" & mstrType
    End If

    If mstrUDH <> String.Empty Then
        strDataString += "&" & "udh=" & mstrUDH
    End If

    If Not mdtDeliveryDate = Nothing Then
        Dim objDeliveryDate As New StringBuilder()
        objDeliveryDate.Append(mdtDeliveryDate.Year)
        objDeliveryDate.Append(Prefix(mdtDeliveryDate.Month.ToString(), 2))
        objDeliveryDate.Append(Prefix(mdtDeliveryDate.Day.ToString(), 2))
        objDeliveryDate.Append(Prefix(mdtDeliveryDate.Hour.ToString(), 2))
        objDeliveryDate.Append(Prefix(mdtDeliveryDate.Minute.ToString(), 2))
        objDeliveryDate.Append(Prefix(mdtDeliveryDate.Second.ToString(), 2))
        strDataString += "&" & "deliverydate=" & Convert.ToString(objDeliveryDate)
    End If

    Dim strReturnValue As String = ""

    Dim xmlReader As New XmlTextReader(String.Format("{0}?{1}", strPostString, strDataString))

    While xmlReader.Read()
        If xmlReader.NodeType = XmlNodeType.Element Then
            Select Case xmlReader.LocalName
                Case "recipients"
                    If True Then
                        mintSuccessCount = Integer.Parse(xmlReader.ReadString())
                        strReturnValue += "recipients : " & mintSuccessCount.ToString() & vbCr & vbLf
                        Exit Select
                    End If
                Case "success"
                    If True Then
                        mblnSuccess = Boolean.Parse(xmlReader.ReadString())
                        strReturnValue += "success : " & mblnSuccess.ToString() & vbCr & vbLf
                        Exit Select
                    End If
                Case "resultcode"
                    If True Then
                        mintResultCode = Integer.Parse(xmlReader.ReadString())
                        strReturnValue += "resultcode : " & mintResultCode.ToString() & vbCr & vbLf
                        Exit Select
                    End If
                Case "resultmessage"
                    If True Then
                        mstrResultMessage = xmlReader.ReadString()
                        strReturnValue += "resultmessage : " & mstrResultMessage & vbCr & vbLf
                        Exit Select
                    End If
            End Select
        End If
    End While

Also, when performing an HTTP request from ASP.NET, it does not appear in Fiddler, while the actual HTTP request happens. How can I track the HTTP fastback from within the ASP.NET engine?

I still don't know what the problem is, but I worked around it by doing the postback via an HttpWebRequest directly. I think the problem was somewhere in the while loop.