I’m developing my own websocket server. It works fine for ws (http) handshake, and now I want to go on, making secured handshake (https) via TLS 1.2. So I need a certificate with private key available to make it run. The websocket server is running standalone without any commercial internet servers, listening to port 80 for ws communication and 443 for https wss communication. The websocket server has a separate IP totally isolated of my web provider, but it will be accessed from a https web page.
Which certificate do I need to use and is it possible to get it from Let’s Encrypt? I need all necessary files to load certificate data by my own, and browsers are satisfied to tell users they have a secured connection.