All the HTTPS services of CONNECT cannot be invoked from .NET technology. All the tools in .NET give the same message (not just our adapter services). the error is: the underlying connection was closed: the connection was closed unexpectedly.
Due to security, CONNECT Https Services (server configuration) server requires clients's certification present to authenticate when ssl handshake happens. This configuration can be turned off on the wildfly server by removing this element "verify-client="REQUIRED" in standalone.xml
I have seen it where even if you set verify-client to REQUEST (or disable it entirely), CONNECT itself will complain. This was in 4.4 I think, I'm not sure if it's different now, but something to look out for. It may be the path of least resistance to have your client present a SSL certificate (if it can).