Who managed to connect https to the prolog directly? https is connected, but incorrectly, the server does not give the root certificate, the certificate chain is incorrectly determined. I connected the certificates that letsencrypt gives. There are no errors on the server, maybe I don’t know something or missed it.
You can do some debugging using openssl.
I did all this and, as I wrote earlier, I discovered that the server does not see the root certificate that I indicated to it. I have cowboy and swi-prolog hanging on different ports, I checked the same certificate. There are no problems with the cowboy, the chain is given correctly, there is a problem with prolog, it does not see ‘caroot’
You find some background info at GitHub - triska/letswicrypt: Prolog HTTPS Servers and in similar work by Markus Triska.
The backend server us.swi-prolog.org runs as a Prolog process directly connected to the http and https ports. According to one of the many ssl config testers it is properly configured and the main thing the tests frowns upon is acceptance of some old standards. As HTTPS for this site is just about the identity of the site (no secret information is ever passed), this is IMO fine.
The site uses library(http/http_unix_daemon).
I succeeded, my mistake was that I gave the server an incomplete chain of certificates, you need to make one file from the root certificate and the certificate for the domain.