Fedora 26 Server: Node.js app hangs forever when not launched directly

I’ve tried to launch a Node.js app either with systemd or cron both with unprivileged and privileged accounts but it seems that the only way to get it work is with node app.js or whatever_monitoring_package app.js. I’m using nginx as a reverse proxy, so my first guess was to check if nginx’s logs had some errors but nothing. Then I tried to launch it directly by http://IP:PORT but nothing. My firewall’s rules are ok, triple-checked. Browsers say “Waiting…”. systemd works normally and cron is normally executed at startup. There are no errors.

Thanks in advance.