Client-side communicate to the Server-Side

Hello All, I am looking for a little advice. I hope this is the correct forum to post this question. Anyhow, I want to build a live video chat application. I am really unsure what is the best alternative to go for, for the users to send text data messages.
I have read tutorials on the the SharedObject.send method and the NetConnection.call() For the client to speak to the Server. However, i am still no clearer in my mind what the difference is? Please forgive me for the simplicity of this question but i am a newbie could these two alternatives work in a chat application were users are constantly send messages back and forth?
Thank You Ricky