How do you ask someone what he or she would prefer to be called? For example, if you are talking to another researcher from a foreign university, how do you ask him or her what title would he or she be preferred to be called by?

"What's your preferred title" sounds too formal.

"What do you like to be called" sounds too informal.

"Can I call you by your first name" sounds too demanding.

"Are you comfortable with me calling you Doctor. John" sounds...awkward.

Can someone please teach me some academic etiquette?
I think that it is best to err on the side of being too formal. I tend to ask after I refer to their name for the first time: "It's so nice to talk with you, Dr. Smith- Do you prefer Dr. Smith or do you go by another name or title?..." Then continue with your conversation.