Real Time Interaction on Web Page

Background: I have a microcontroller ESP8266 that enable connexion through TCP/IP, UDP or even HTTP stack using WiFi. A button is connected to this microcontroller and trigger event on touch. I send that information (now in UDP for test) towards a computer which runs an HTML carousel (web page). I would like to create the interaction between the button and the web page in real-time. I found that a simple HTML/CSS/JS web page doesn't allow to read UDP socket so I install a web server on the computer to use PHP.

NB: Real-time means direct interaction (inferior to 30 ms up to 100 ms) but should be ok in the actual data flow.

Problem: I struggle on the Web implementation. I found appropriate carousel in HTML/CSS/JS. I already received some UDP packet in a PHP file but I don't know how can I perform a real-time interaction (trigger image change in the carousel). I read about Ajax but it seems to be at client-side. I have in fact no background in Web application design.

I would like to know if in fact, it is possible and if yes basic information to start working on it.