SiteToSiteClient.Builder allows setting an SSLContext or setting all of the individual SSL properties, it then has a method getSSLContext() which says that if the sslContext is null return that, otherwise use the properties to create one:
The problem is this getSSLContext() is never called. When the builder's build() method is called, it passes the builder to StandardSiteToSiteClientConfig and just assigns all the member variables with direct access:
Later on in SocketClient it will call SiteToSiteClient.getSSLContext():
This will still be null here if only the SSL properties were initially specified on the builder, and therefore won't end up creating an Https connection and thus failing.