PayPal TLS 1.2 upgrade issues - paypal

Question

With the PayPal TLS 1.2 upgrade looming, I'm in a rush to upgrade my clients payment system. The problem is, they are on .NET 3.5. I've talked to PayPal support and they said that their SDK only supports .NET 4.5. To upgrade the entire site to 4.5 will take an EXTREMELY long time to complete. So unless they are wrong and someone can point me in the right direction on how to implement the payflow pro SDK into a .NET 3.5 system, I have come up with 2 options (aside from an upgrade):
Use WebClient to connect to the payflow gateway. I like this solution but I'm not getting a response. I have two snippets of code
using (System.Net.WebClient wc = new System.Net.WebClient())
{
wc.Headers.Add("Content-type", "text/namevalue");
wc.Headers.Add("Content-Length", requestData.ToString().Length.ToString());
wc.Headers.Add("X-VPS-Timeout", "30");
wc.Headers.Add("X-VPS-Request-ID", System.Guid.NewGuid().ToString());
wc.Headers.Add("X-VPS-VIT-Client-Type", "PHP/cURL");
string HtmlResult = wc.UploadString("https://" + this.HostAddress, requestData.ToString());
}
and
System.Net.HttpWebRequest httpWebRequest = (System.Net.HttpWebRequest)System.Net.WebRequest.Create("https://" + this.HostAddress);
httpWebRequest.ContentType = "text/namevalue";
httpWebRequest.ContentLength = rawRequestData.Length;
httpWebRequest.Headers.Add("X-VPS-Timeout", "30");
httpWebRequest.Headers.Add("X-VPS-Request-ID", System.Guid.NewGuid().ToString());
httpWebRequest.Headers.Add("X-VPS-VIT-Client-Type", "PHP/cURL");
httpWebRequest.Method = "POST";
using (var stream = httpWebRequest.GetRequestStream())
{
stream.Write(rawRequestData, 0, rawRequestData.Length);
}
var response = (System.Net.HttpWebResponse)httpWebRequest.GetResponse();
var stringResponse = new System.IO.StreamReader(response.GetResponseStream()).ReadToEnd();
both are returning empty response exceptions.
The alternative is to create a local webservice that's compiled in .NET 4.5 and have the web app consume it to process transactions. This will all be done locally, so it's not like the web app is communicating with another computer, it will be connecting to a webservice that is local. As for the webservice, I'll make it respond only to local requests. The problem is that there won't be an SSL on the web service. So the big question is, if the webservice doesn't respond to external requests, requests are made internally, will it break PCI compliance?

Answer 1

I have not had to resort to this because the apps I maintain are 4.5 or higher but
"The .NET framework version 3.5.1 and earlier versions did not provide support for applications to use Transport Layer Security (TLS) System Default Versions as a cryptographic protocol. This update enables the use of TLS v1.2 in the .NET Framework 3.5.1."
https://support.microsoft.com/en-us/help/3154518/support-for-tls-system-default-versions-included-in-the-.net-framework-3.5.1-on-windows-7-sp1-and-server-2008-r2-sp1