nginx/cocalc.conf

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name calc.exozy.me;

    ssl_certificate /etc/letsencrypt/live/exozy.me/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/exozy.me/privkey.pem;

    location / {
        # push traffic through the proxy to the port you mapped above, in this case 9090, on the localhost:
        proxy_pass https://localhost:6969;

        # this enables proxying for websockets, which cocalc uses extensively:
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
        proxy_set_header Host $host;

        client_max_body_size 1G;
    }
}