server {
    listen 443 ssl;

    # Domain names this server should respond to.
    server_name SUBDOMAIN;

    # Load the certificate files.
    ssl_certificate         /etc/letsencrypt/live/uptime/fullchain.pem;
    ssl_certificate_key     /etc/letsencrypt/live/uptime/privkey.pem;
    ssl_trusted_certificate /etc/letsencrypt/live/uptime/chain.pem;

    # Load the Diffie-Hellman parameter.
    ssl_dhparam /etc/letsencrypt/dhparams/dhparam.pem;

    #return 200 'uptime';
    #add_header Content-Type text/plain;

    location / {
        proxy_set_header   X-Real-IP $remote_addr;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header   Host $host;
        proxy_http_version 1.1;
        proxy_pass http://FULLY_QUALIFIED_DOMAIN_NAME_OF_HOST:3001;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
}