Question

{Following is the vb.net code for IPN listener:
    If Me.TestMode = True Then
            Me.RequestUrl = "https://www.sandbox.paypal.com/cgi-bin/webscr"
        Else
            Me.RequestUrl = "https://www.sandbox.paypal.com/cgi-bin/webscr" '"https://www.paypal.com/cgi-bin/webscr"
        End If



        '====================================Test======================================'
        Dim startTime As String = String.Format("{0:MM-dd-yyyy hh:mm:ss:tt}", Now)
        '=============================================================================='

        Dim req As HttpWebRequest = CType(WebRequest.Create(Me.RequestUrl), HttpWebRequest)
        req.Method = "POST"
        req.ContentType = "application/x-www-form-urlencoded"
        Dim Param() As Byte = HttpContext.Current.Request.BinaryRead(HttpContext.Current.Request.ContentLength)
        Dim strRequest As String = Encoding.ASCII.GetString(Param)
        strRequest = strRequest & "&cmd=_notify-validate"
        req.ContentLength = strRequest.Length
        ' Dim pairs() As String = strRecieved.Split("&")
        Using streamOut As StreamWriter = New StreamWriter(req.GetRequestStream(), Encoding.ASCII)
            streamOut.Write(strRequest.ToString)
            streamOut.Close()
        End Using
        Dim streamIn As StreamReader = New StreamReader(req.GetResponse().GetResponseStream())
        Dim strResponse As String = streamIn.ReadToEnd()
        streamIn.Close()
        WriteLog(strResponse)

I have done code for paypal IPN listener in vb.net . When I test that url with paypal sandbox account, it shows following message:
“IPN successfully sent.”
But when I check my log file on server, then it shows INVALID response from paypal sandbox url. Without VALID response my other code will not work.
Please help!!

Answer 1

Generate paypal transaction like e.g buy now button via vb.net

Public Shared Function GetPayPalPaymentUrl(item_name As String, item_number As String, amount As String, quantity As String, username As String) As String
Dim strURL As String = "https://www.sandbox.paypal.com/cgi-bin/webscr"
If PaypalBLL.Paypal_Live_Status() = 1 Then
    strURL = "https://www.paypal.com/cgi-bin/webscr"
End If
Dim BaseUrl As String = Config.GetUrl()
Dim cancel_url As String = BaseUrl + "paypal/cancel.aspx"
Dim return_url As String = BaseUrl + "paypal/confirmation.aspx"
Dim notifyUrl As String = BaseUrl + "paypal/ipn.aspx"
'string image_url = ""
Dim image_url As String = ""
' paypal header url
Dim paypal_logo As String = HttpUtility.UrlEncode(BaseUrl + "images/logo.png")
Dim Url As New StringBuilder()
Dim CustomFieldValue As String = username
'User-defined field which PayPal passes through the system and returns to you in your merchant payment notification email. Subscribers do not see this field.
Url.Append(strURL + "?cmd=_xclick&upload=1&rm=2&no_shipping=1&no_note=1&currency_code=USD&business=" + PaypalBLL.Paypal_Receiver_Email() + "&item_number=" + item_number + "&item_name=" + item_name + "&amount=" + amount + "&quantity=" + quantity + "&undefined_quantity=0&notify_url=" + notifyUrl + "&return=" + return_url + "&cancel_return=" + cancel_url + "&cpp_header_Image=" + image_url + "&cpp_headerback_color=ECDFDF&cpp_headerborder_color=A02626&cpp_payflow_color=ECDFDF&image_url=" + paypal_logo + "&custom=" + CustomFieldValue + "")
Return Url.ToString()
End Function

Generate paypal link, when you click on link, you will be redirect to paypal sandbox or live link. once you complete transaction, you will be redirected to website back and within background paypal will send transaction event via ipn.

Hope you will receive proper ipn response.