Problems With Paypal Express Checkout Integration (WEBREQUEST)

Question

So I was struggling with making head or tail out of the PayPal documentation and always felt that something was not right with my Webrequest.

So I stripped all the code back to basic and simply submitted the request via HTTP and the PLUS side is that I now get a response back from the PayPal sandbox server where ACK=Success and TOKEN=Valid-token-value-here there are some other variables returned too, such as CORRELATIONID and TIMESTAMP.

And hence so I tried some of the webrequest samples and I simply get a blank screen instead of being redirected to Paypal for the (sandbox) customer to complete payment.

So if anyone can post their WebRequest method that would be great.

Here is the code I used for my webrequest, I'm sure its wrong but cannot pinpoint where it is going wrong.

Also, when I run the code on my localhost during debugging, everything works fine and the call is completed with SUCCESS and a TOKEN is received.

When I run it live, I recieve Error Number 5 in the Error exception and also the text `Remote host failed to connect' in the STATUS DESCRIPTION.

THIS IS THE UPDATED CODE

Function MakeWebRequest(ByVal pUseSandbox As Boolean, ByVal pRequestMethod As String, ByVal pReturnUrl As String, ByVal pCancelUrl As String, ByRef pRtnStatus As String, ByRef pRtnStatusId As HttpStatusCode, ByRef pRtnResponseString As String) As Boolean
'
Dim _sxHost As String = Nothing
Dim _sxEndpoint As String = Nothing
Dim _sxNameValCol As System.Collections.Specialized.NameValueCollection = Nothing
Dim _sxResponseCol As System.Collections.Specialized.NameValueCollection = Nothing
Dim _sxCounta As Integer = Nothing
Dim _sxParamsString As String = Nothing
'
'-> Init
_sxParamsString = ""
MakeWebRequest = False
_sxNameValCol = New System.Collections.Specialized.NameValueCollection()
_sxResponseCol = New System.Collections.Specialized.NameValueCollection()
If pUseSandbox Then
  _sxHost = "http://www.sandbox.paypal.com"
  _sxEndpoint = "https://api-3t.sandbox.paypal.com/nvp"
Else
  _sxHost = "http://www.paypal.com"
  _sxEndpoint = "https://api-3t.paypal.com/nvp"
End If
'-> Create Request
Try
  '-> Key/Value Collection Params
  _sxNameValCol.Add("METHOD", "SetExpressCheckout")
  _sxNameValCol.Add("USER", _UserName)
  _sxNameValCol.Add("PWD", _Password)
  _sxNameValCol.Add("SIGNATURE", _Signature)
  _sxNameValCol.Add("PAYMENTREQUEST_0_AMT", Format(_Basket.BasketTotalIncDelivery / 100, "0.00"))
  _sxNameValCol.Add("PAYMENTREQUEST_0_PAYMENTACTION", "Sale")
  _sxNameValCol.Add("PAYMENTREQUEST_0_CURRENCYCODE", "GBP")
  _sxNameValCol.Add("RETURNURL", pReturnUrl)
  _sxNameValCol.Add("CANCELURL", pCancelUrl)
  _sxNameValCol.Add("REQCONFIRMSHIPPING", "0")
  _sxNameValCol.Add("NOSHIPPING", "2")
  _sxNameValCol.Add("LOCALECODE", "EN")
  _sxNameValCol.Add("BUTTONSOURCE", "PP-ECWizard")
  _sxNameValCol.Add("VERSION", "93.0")
  '-> UrlEncode
  For _sxCounta = 0 To _sxNameValCol.Count - 1
    If _sxCounta = 0 Then
      _sxParamsString = _sxParamsString & _sxNameValCol.Keys(_sxCounta) & "=" & HttpUtility.UrlEncode(_sxNameValCol(_sxCounta))
    Else
      _sxParamsString = _sxParamsString & "&" & _sxNameValCol.Keys(_sxCounta) & "=" & HttpUtility.UrlEncode(_sxNameValCol(_sxCounta))
    End If
  Next
  '-> Credentials (not used)
  '_sxRequest.Credentials = CredentialCache.DefaultCredentials
  Try
    Dim _sxRequest As WebRequest = DirectCast(System.Net.WebRequest.Create(_sxEndpoint), System.Net.HttpWebRequest)
    '-> Convert request to byte-array
    Dim _sxByteArray As Byte() = Encoding.UTF8.GetBytes(_sxParamsString)
    _sxRequest.Method = "POST"                                                      'Our method is post, otherwise the buffer (_sxParamsString) would be useless
    _sxRequest.ContentType = "application/x-www-form-urlencoded"                    'We use form contentType, for the postvars
    _sxRequest.ContentLength = _sxByteArray.Length                                  'The length of the buffer (postvars) is used as contentlength
    Dim _sxPostDataStream As System.IO.Stream = _sxRequest.GetRequestStream()       'We open a stream for writing the postvars
    _sxPostDataStream.Write(_sxByteArray, 0, _sxByteArray.Length)                   'Now we write, and afterwards, we close
    _sxPostDataStream.Close()                                                       'Closing is always important!
    '-> Create Response
    Dim _sxResponse As HttpWebResponse = DirectCast(_sxRequest.GetResponse(), HttpWebResponse)
    '-> Get Response Status
    pRtnStatus = _sxResponse.StatusDescription
    pRtnStatusId = _sxResponse.StatusCode
    '-> Reponse Stream
    Dim _sxResponseStream As Stream = _sxResponse.GetResponseStream()               'Open a stream to the response
    '-> Response Stream Reader
    Dim _sxStreamReader As New StreamReader(_sxResponseStream)                      'Open as reader for the stream 
    pRtnResponseString = _sxStreamReader.ReadToEnd()                                'Read the response string
    MakeWebRequest = True
    '-> Tidy up
    _sxStreamReader.Close()
    _sxResponseStream.Close()
    _sxResponse.Close()
    _sxByteArray = Nothing
    _sxPostDataStream = Nothing
    _sxRequest = Nothing
    _sxResponse = Nothing
    _sxResponseStream = Nothing
    _sxStreamReader = Nothing
  Catch ex As Exception
    pRtnStatusId = Err.Number
    pRtnStatus = "response(" & ex.Message & ")"
    Decode(pRtnResponseString, _sxResponseCol)
    pRtnResponseString = Stringify(_sxResponseCol)
  End Try
Catch ex As Exception
  pRtnStatusId = Err.Number
  pRtnStatus = "request(" & ex.Message & ")"
  Decode(pRtnResponseString, _sxResponseCol)
  pRtnResponseString = Stringify(_sxResponseCol)
End Try
'-> Tidy Up
_sxHost = Nothing
_sxEndpoint = Nothing
_sxNameValCol = Nothing
_sxResponseCol = Nothing
_sxCounta = Nothing
_sxParamsString = Nothing
'
End Function

Answer 1

OK, so it's now clear that you're not getting any response from the server because your server isn't able to connect to PayPal's servers at all. Hence, you got no server-response and the message Unable to connect to the remote server. When I tested, I got a HTTP 200 response with the following body:

TIMESTAMP=2015-07-07T09:07:39Z&CORRELATIONID=7f4d2313c9696&ACK=Failure&VERSION=93.0&BUILD=17276661&L_ERRORCODE0=10002&L_SHORTMESSAGE0=Authentication/Authorization Failed&L_LONGMESSAGE0=You do not have permissions to make this API call&L_SEVERITYCODE0=Error

Obviously that's because I tested with a blank username and password.

So, something is wrong with your server setup that's preventing you from making outside connections, either at the IIS level or due to your firewall configuration.

Without physically being present at your machine, there's not a lot we can do to track down what's blocking it, but you can try opening HTTP requests to other public websites like Google.com and see if those succeed.