How do you get a guys attention online whom you've known for years, but haven't talked to lately?

I want to talk to a guy that I haven't talked to in years. We were never close but I'd like to get together with him sometime. How can I "non-chalantly" talk to him and see if he's interested? Sure I could be bold and just ask him straight out--but I really don't know him well enough to be that straightforward.