Hello,

What I would suggest here is to use Nginx as a reverse proxy, so that way you could access your application directly on https://sub.name.com rather than having to specify your port at the end.

That way you will be able to use Let’s Encrypt together with Nginx.

Your Nginx Server block would look something like thins:

server {
    listen 80;
    server_name sub.name.com;

    location / {
        proxy_set_header   X-Forwarded-For $remote_addr;
        proxy_set_header   Host $http_host;
        proxy_pass         http://127.0.0.1:3002;
    }
}

Then you could use certbot to issue your Let’s Encrypt SSL, it should also automatically create the Nginx Server block for port 443 for you as well, you can follow the guide here:

https://www.digitalocean.com/community/tutorials/how-to-secure-nginx-with-let-s-encrypt-on-ubuntu-16-04

Hope that this helps!
Regards,
Bobby