We have an iOS app that connects to our server through HTTPS. When the app is built with the new iOS 9 SDK and ran under iOS 9, the following error occurs:
NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9802)
iOS9 requires the server to only support TLSv1.2 and support perfect forward security.
Also required is for the app to support IPV6 including not using hard-coded IP addresses. Suggested is to use
NSURLSession. Otherwise exception additions must be made in the app plist.
See the WWDC-15 session "Security and your Apps".
Also see Steven Peterson's Blog for details.