What does "aye" means in text?

Anonymous
So we are from the US. I was texting a pretty good guy friend of mine and he said he needs me to help him with his homework because he's stuck in a problem since we're in the same class. We are both out of class at 3 and always available after that time so i was like "So what place do you wanna meet tmr at 3 so I can help you with that?" and he replied "Aye what's up with you". What does that suppose to mean? What does "aye" means? And why is he saying what's up with me to me it's like "what's wrong with you" why would he say that it's really weird so I guess I misunderstand the meaning of what he said. Helpppp.
What does "aye" means in text?
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