Guy help!

So I’ve just recently become single a couple weeks ago and I’m not sure how people are finding out but a guy from school that I’ve never talked to keeps trying to message me. He was good friends with my ex years ago but I never met him properly.. now he’s sent me a message saying “hey, was wondering if you were up for a chat sometime?” I’m not interested in him at all but I don’t want to be mean or hurt his feelings. What do I do or say? I don’t want to say I’m not interested because he’s never actually said he wants to date me but It seems like that’s what he’s trying to do.