How do a website check if client system (running kali linux) is connected to internet?

I want to make a webpage which will continuously check if my client system (only single client, a Rpi3 running kali linux) is connected to Internet or not, just like whatsapp web, which displays error message "Phone is not connected" if the device is not connected to internet.

I know this can be done for Android but can it be done for a linux based client just like ping??

I want to continuously communicate a webpage with respberry pi 3 modal B to control the devices connected to Rpi via the webpage.

Commands given through webpage must reach to RPi and if RPi is not connected to internet it should display a message indicating to check the RPi.

Is there any way to check that? If yes then how can i achieve it. Note: The webpage will be uploaded on free hosting website (000webhost.com) and it does not provide cron job sceduled less than 10 min. Please help. Thankyou.