Does it have to be HTTP request? If your server can handle SSE you can use those to trigger certain actions. If validation is succesful, you could call a “open door” function.
Webhooks might also be of interest, since those can make certains requests for you.
What kind of server setup are you using? LAMP stack, or some fancy Node.js perhaps?
Also, check out this awesome project as well, since it sounds (very) similar:
There’s a video of it in action on the bottom. Seeing as you’re dutch, you should be able to understand the German 