SSLSocket certificate under Windows

The SSLSocket docs say that when using macOS/Linux, the public and private keys need to be combined into one file, and if I do that then my app works OK (I wire the cert file in using the CertificateFile property).

This Desktop app has an HTMLViewer which communicates with the rest of the app (the Xojo side) using a websocket server built into the app. In the Viewer it connects in the javascript. This works fine if the socket is not used in secure mode (both macOS and Windows), and so far in secure mode under macOS. But how do I do it in Windows? Can I use the same pair of self-signed certificates that I use for macOS? The docs don’t say which of the key files needs to be wired to CertificateFile, or what to do with the other one.