In several English books and films I have noticed, that some people call others "son", even though they are not related.
Like teachers say it to their students, or Military guys to other military guys or not military guys and (as English is obviously not my first language) I try to find out the scheme.

Is this still common or old-fashioned?
In which "scene" is/was this ususal? (Like do mainly people in uniforme use this or is it a more general thing) And where (greographically) do people use that form of adress? (Like is it a general anglophone thing or is it just current in the US or somewhere?)
And does the person who calls another son needs to be (noticeably) senior or does he needs to have a higher rank?
Oh, and does there exist an equivalent with "daughter"?

I know, that are a lot of questions, and probably a lot of writing mistakes, but I couldn't find any answers in the Internet yet and this really interests me.