It's something that needs to be emphasized a lot: If you send somebody a text, and expect them to answer on your timetable, not theirs, you're both going to have a bad time.
Start with expectations. Actually get on the phone and have a conversation about what you both expect, communications-wise. Get on the same page for what's "reasonable"; if one or the other of you is stuck at work, or something along those lines, then "reasonable" can be a bit more fluid than you might think.
Finally, have some patience. Nobody can be on top of their phone constantly. If you find yourself getting aggravated, take a deep breath and try to think better of him.