> “What’s up?” is one of the most dreadful texts to get; it’s short for “Hello, I’d like you to entertain me now.”
The typical response to "What's up?" from myself and, uh, nearly everyone I know, is some variation on
"Not much! What's up with you?" or
"[trivial recent happening, quickly related] So, what's been going on with you?"
...and that's because "What's up?" is nearly universally a way to prompt someone to ask you that question back, so you can tell them about the thing you really want to say without it seeming sudden or forced.