Socrates, the Sophist?

Aristophanes has these wonderful portraits of Socrates which are clearly very, very different from anything our other sources say about Socrates. So which of them to believe and what do they have in common? And one notable thing about Aristophanes, Aristophanes clearly thinks that Socrates is the Sophist and that he's perverted tragedy. He's spoiled tragedy by getting into Euripides mind. I'd want to go wider than that but indeed philosophy is a focal point for M.M.S.'s work. Apart from that attitude, what did Socrates himself centrally believe philosophically speaking? It's quite difficult to answer that question.