nginx-localtunnel.conf

proxy_http_version 1.1;

# http://nginx.org/en/docs/http/websocket.html
map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

upstream server {
    server 127.0.0.1:9876;
}

server {

    server_name tunnel.intesso.io *.tunnel.intesso.io;

    listen 80;
    listen [::]:80 ipv6only=on;

    location / {
        proxy_pass http://server/;

        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Proto http;
        proxy_set_header X-NginX-Proxy true;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;

        proxy_redirect off;
    }
}

server {

    server_name tunnel.intesso.io *.tunnel.intesso.io;

    listen 443 ssl http2;
    listen [::]:443 ipv6only=on;

    ssl_certificate /etc/letsencrypt/live/tunnel.intesso.io/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/tunnel.intesso.io/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

    location / {
        proxy_pass http://server/;

        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header X-NginX-Proxy true;
        proxy_set_header Connection $connection_upgrade;

        proxy_redirect off;
    }
}