Let's say if you make an online game with RMXP, you'll be the first one. Seriously, Beyond DOES let you make online games, and there are tens of completed, working, stable, games made with it. Why don't you try it out? it's free.
You can also try Game Maker, I'm not sure how easy it is, but there are online games made with it, and it's cheap(20$). You may also wanna try the professional program called Multimedia Fusion 2 (MMF2).
If you must use RMXP, well, don't make an online game.
Also, this isn't the place to ask for support, you better make a new topic.