SMS HTTP API call from ASP.NET is slow - asp.net

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.