Is it possible to have a web app do local syncing over a LAN when there is no internet connection?

Question

So I want to develop a web app (ANGULAR) that will be able do work fine even without internet and then do "push/pull" requests when connected to the internet and communicate with other computers over a LAN.

So for the problem of one computer I found a solution using indexdb (NgIndexedDb in this case) and I think it will work fine

But this doesn't solve the LAN issue What I want is to be able to send requests and every user of the app is impacted by each request. For example if an article is created and stored in the database all the users should be aware that the article has been created I don't know if it means doing the same request over all the computers but it should be perceived by every LAN user

Another example if a ressource that can be used by only one user at the time is used by a certain user, another user in the LAN shouldn't be able to use it

I tried to do some research on that with no success

Any help would be appreciated even if it means using a backend

Thanks in advance