fsockopen doesnt resolve behind synology reverse proxy

[opicron]

When I open the resourcespace url w/o config.php prefilled I get /pages/setup.php but I can not save. It always returns to /pages/setup.php with this error:

[Mon Jan 19 20:00:14.460832 2026] [php:warn] [pid 17] [client 172.27.0.1:52466] PHP Warning: fsockopen(): Unable to connect to ssl://[mydomain]:443 (Connection timed out) in /var/www/html/pages/setup.php on line 80, referer: http://[mydomain]:8222/pages/setup.php

I am running a reverse proxy to get this working. Which works for all my other dockers. Somehow this docker doesnt like a reverse proxy?

[opicron]

Edit: no matter how I configured the reverse proxy or the firewall (also disabled the firewall) I could not make it work. What eventually worked was to change url_exists function in setup.php and return true.

Only then I could pass the setup and the setup works. E.g. I am logged in now.. Maybe the websocket check in setup should be overridable?

[opicron]

Alright, I was able to loopback the domain to synology with this docker-compose.override.yml:

services:
  resourcespace:
    ports: !override
      - "8222:80"
    extra_hosts:
      - "[reverse proxy domain]:host-gateway"

Hopefully this will help someone too.