How long befote foreclosure after docket mumber is established?

You may be confusing foreclosure with bankruptcy. In states that require a court action before foreclosure, you will get the notice with the court's docket number and can respond appropriately.

In states that rely on open and public seizure, there may be no legal action, so no docket number. Someone from the mortgagee will show up and walk on your property and declare it has been seized. Usually, the mortgagee has to publish its intent to seize in a local newspaper.

Some states require the mortgagee to file an action to determine that the debtor(s) is (are) not on active duty in the military. The debtor(s) get notice of that, with the docket number. If no debtor is on active duty, there is nothing s/he can do to respond.