So, I have been talking to this guy for about a month and I've known him for about a year. I haven't really hung out with him yet, but my question is how can you tell someone likes you, through an online relationship?

It sometimes can be hard to tell, but my advice is to start hanging out with him because people are completely different in person than online (I know from experience). If you keep talking to him online you can sometimes tell if they like you if they ask you a lot of questions about your life and what your doing at that moment. Hope this helps!