How does the popup wifi authorization window work?

Question

WiFi

Good afternoon. Tell me, how does the window that pops up after connecting to a wi-fi network work? The so-called sudden window or popup. I understand that the device sends a request to the gateway, but who is responsible for displaying and processing it? with the http redirect in the browser, everything is clear, but who throws this unexpected page? Authorization server?

Answer 1

This is called captive portal. Pings are used to windows, apple, android services, etc. to determine if the packet has changed (whether the IP changes when trying to get other URLs) and if it does, a window is displayed. I was developing a firmware for the townwifi.ru service (WiFi authorization via SMS and social networks), I just did it with and without a confirmation window (redirect from the first access in the browser)