How to make a stateful web service?

Question

JavaScript

How to make a web service (service) from which it would be possible to request a state.
The web service is simple - it receives parameters in xml format and returns a binary file. The catch is that the process can be long, it would be great to be able to find out what state the service is in (display the progress bar on the client, display the current operation).
How can this be done in relation to .Net?
As a bad solution, I see an asynchronous launch of a service that will log its actions, for example, in a database and a log file, and the web client will periodically read these logs, displaying them to the user.

Answer 1

That's pretty much how it's done. The service writes to the database/queue - the client reads by id and displays all/last

Answer 2

By the way, what about WebSockets?