WinHttp TLS connection in classic asp

Question

I'm trying to send payment data to SagePay and, as they are turning off SSL, it needs to be sent using TLS.

The code I have is as follows:

set httpRequest = Server.CreateObject("WinHttp.WinHttprequest.5.1")
httpRequest.Open "POST", CStr(strPurchaseURL), false
httpRequest.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
httpRequest.send strPost
strResponse = httpRequest.responseText

I've been told that adding an option lets you set the protocol used but the only one I've found is:

httpRequest.option(9) = 2720

which allows for TLS and SSL but it can only be TLS, does anyone know what the code needs to be or is there something else I should be doing.

Answer 1

Option 9 is WinHttpRequestOption_SecureProtocols which is

SSL 2.0: 0x0008
SSL 3.0: 0x0020
Transport Layer Security (TLS) 1.0: 0x0080

So

httpRequest.option(9) = &H80

Answer 2

If you are on Windows Server 2003 you may be having the same problem I was having - if you have access to the server, try the answer I added to my own question here: https://stackoverflow.com/a/29140418/1081692 and see how you get on.