Is there a way to communicate with someone while they are dreaming?

Hi! Very curious to hear about your conclusions if you ever read this...

From what I've heard there are some accounts of astral travelers being able to see someone in the dream that person is having. Most reports however state that the person they try to reach (the one having the dream) is in a zombie-like state where they don't deem entirely conscious. Even if this is the case, it can be interesting to see what other people dream about, Whether this is or isn't ethical is a very real question one needs to consider though. I can't stop you from trying however. Good luck with it!

What about if the other person is doing astral travel too?

There have definitely been accounts of people meeting in the astral, I encourage you to look them up as they're quite interesting. So yes, you should be able to communicate with them in the astral if they are consciously projecting.