Online Flash Game

Hello,

I’m Mark and I am quite new in this world.

Recently I just made a simple (or not that simple) game with flash cs4 and actionscript3, but obviously is only playable in local.

My question is, now if I would like to make it an online game so people could connect through internet to some kind of server and play against each other, which tools/programs/languages would be necesary?

How the communication between clients and server would be?

Finnaly, how dificult it would be: easy, average, hard or impossible?

Online probably meaning creating maybe a chat room where you could challenge other players…etc

Hope you get the idea, any help is so appreciated, really.
Thanks.

Mark