Online schematic editor for multiple concurrent users. Implementation?

Question

PHP

You need to create an online "board" so that several users can work on the diagram at the same time.
For drawing I will use fabric.js , but there is no experience of implementing "SIMULAR WORK" for several users.
Read about comet servers. This is a paid item. Again, constantly updating boards for all connected users is a more resource-intensive task than a simple chat.
In general, I will be grateful for any ideas and considerations on the topic.
Thanks

Answer 1

What is usually used in practice for collaboration on documents https://ru.wikipedia.org/wiki/%D0%9E%D0%BF%D0%B5%D...
Well, you can implement communication via web sockets , for example socketo.me

Answer 2

From the point of view of the server comets, your task is no different from a regular chat. The Comet server just sends messages and doesn't care if it's human-readable text or technical data wrapped in JSON.
You do not need to transfer all the text through the comet server, but only the change commands generated by users, and they will not be of great length according to the idea.
For example, if you look at this service https://comet-server.ru , then there is a free tariff for up to 20 people online that the harm should be enough to start the project.
Here is an example of building a chat , and there is also the ability to send messages from user to user , taking into account authorization data, but at the same time directly through the comet server bypassing your servers