The following features have been added in version 5.1 of WinHTTP:
- IPv6 support.
- AutoProxy capabilities.
- HTTP/1.0 protocol, including support for keep-alive (persistent) connections and session cookies.
- HTTP/1.1 chunked transfer support for HTTP responses.
- Keep-alive pooling of anonymous connections across sessions.
- Secure Sockets Layer (SSL) functionality, including client certificates. Supported SSL protocols include the following: SSL 2.0, SSL 3.0, and Transport Layer Security (TLS) 1.0.
- Support for server and proxy authentication, including integrated support for Microsoft Passport 1.4 and the Negotiate/ Kerberos package.
- Automatic handling of redirects unless suppressed.
- Scriptable interface in addition to the API.
- Trace utility to help troubleshoot problems.
If you have Window 2012 server then set objHttp.option (9)to 2720
objHttp.option (9) = 2720
Reference help pages are as follows
https://forums.iis.net/t/1220682.aspx?ServerXMLHTTP 6 0 WinHttpRequest connecting to TLS 1 2 server
