I have a bitnami instance running apache, for which I've generated a letsencrypt certificate using bncert tool. I would like to run a websocket server implemented with node.js on the same instance, but to create a SSL websocket instance I need to provide it 2 .pem files, one for certificate and 1 for key.
Can I re-use the certificate and key I've already generated for my domain, or do I need to generate a new certificate? If it can be reused, where to I find .pem files? If I need to generate a new one, how do I do it for a domain I've already generated certificate for?