Regarding web development using Angular 10 and ASP Net Web api

Question

Dear All,

I hope everyone is well. I have built a web application using ASP .Net WEB Api and Angular 10.

I have a user module in that, I am not maintaing any data regarding logged in user.

I have two queries.

1) E.g. I have a client which has total no of users = 20

but the client has taken software license for 15 users only.

So, Out of 20 user any 15 user can logged in to the systems but not more than that.

How can i do this? How can I restrict no of users logged in to the system for that client?

My second query is,

2) If any user closes the application browser then the system should allow their(Client's) user to logged into system only if number of users logged in are not equal to 15 (license for 15 user only)

Currently, If any user closes browser without logging out of systems properly and if that user again tries to login the system; system shows message like "User is already logged in". In that case; I have to restart IIS so that, that user can login again.

How can I handle these two issues?

Thanking You,

Regards.