Turn based games strategy games have a resurgence in popularity and become things passed down the family.
"See this knight? My great-grandfather recruited it into this CIV V game 72 years ago. Now it is time for it to fulfil its destiny and crush the archer built by the Bob's great uncle"
I think the interstellar protocols would have to be redesigned around UDP, because a reliable protocol would have too many round-trips and would be intolerably slow.
It is possible to engage in constant communication even with a very long delay. Simply both start sending questions of a certain theme, and after the one-way time you can have a fluid conversation, albeit the theme of conversation will change very slowly.
