How to list running screen sessions?

Question

I have a bunch of servers, on which I run experiments using screen. The procedure is the following :

1. ssh to server XXX
2. launc

Answer 1

While joshperry's answer is correct, I find very annoying that it does not tell you the screen name (the one you set with -t option), that is actually what you use to identify a session. (not his fault, of course, that's a screen's flaw)

That's why I instead use a script such as this: ps auxw|grep -i screen|grep -v grep