How to share the same screen in your browser

There is a web service that has the following characteristics in the browser:
Please let me know when you know what kind of technology you can use.

This is a web service created by an acquaintance, but I don't know the elemental technology because he is out of touch.

----- WEB SERVICE IMAGE----

Share the same screen on your browser and
Share the motion of objects such as images and cards on two separate PCs.

The screen looks like a canvas and
You can arrange, move, resize, and delete images and cards.
イメージImagically, please think that several cards are arranged on the board like cards.
　You can move, resize, or delete each card.

Move images and cards on one PC and
on the other PC browser The card moves almost simultaneously.
However, the mouse does not appear on the other PC.

Move, resize, and delete are reproduced almost simultaneously, with little time lag.
I'm sure I'm posting information to the server, but
Is it possible to reload in real time on the other PC only with the so-called Ajax?

What I feel is that reloading image coordinates from the database in real time is
I think there is a limit to the speed.

The server uses a regular rental server and
It seems that the push from the server side like node.js is not used.

Some questions may be a little off the mark, but
I would appreciate it if you could reply.