Modern web services are served on port 443 over HTTPS with secure certificates, not on port 80 over HTTP.

Make sure you have a cert issued and installed for your server, that port 443 is not blocked by any firewall and that curl is explicitly connecting to https.

There’s no indication that running caddy in a container was a problem here.

For a high security context, you would want to figure out private inter-pod networking.

For what you describe, host networking sounds OK.