What is correct On a server or in a server?

No. It isn't. Haven't you swum in the other pool yet? Answer: Although I don't like to disagree, and it's certainly true that in traditional written English we should say 'haven't you swum..', people do use 'you haven't swum..' with a rising intonation in spoken English to express surprise. The questioner may be asking about the declarative sentence 'You haven't swum in the other pool yet.' The question mark relates to the inquiry about grammar, and not necessarily to the function of the construct. As a declarative sentence, it is correct.