Possible to check for (and maybe even connect to) a running server from elisp?

[quodlibetor]

I have `(server-start)' in my .emacs, and sometimes I forget that I've
got an emacs daemon running or that I started it from a detached
screen instance.

I would mostly prefer to be able to just connect to a running server
if it exists, but I'm assuming that the existence of emacsclient means
that's not possible.

Is there, though, a way to at least check if the server is running, so
that I can not call (server-start)?

Or, alternatively, is it possible to start emacscllient without a
file? I normally start into an org agenda-view buffer and choosing a
file to start in is mildly irritating.

quodlibetor)