Does he have the right to tell me who I can and cannot spend time with, given the scenario?

My boyfriend and I have been dating for a year and a half now. A couple months ago (after not talking for 2 years), my ex and I started talking. He asked me out to dinner to show me the restaurant he was working at, at the time. I agreed, thinking it was not a big deal because we were just going to catch up. The dinner was nice, very casual and there were no strings-attached--just like 2 friends going out to dinner. Now, my boyfriend is furious that I did this--not only go to dinner but that I have started talking with my ex-boyfriend. I believe I have the right to spend time with whoever I'd like, while he thinks it's inappropriate and gets very jealous.