Beginner questions

Hi!

I'm a very beginner. So please help a little. I want to call two host 
and connect them. I think how it's work:
1. Sip connection class create the factory objects
2. From SipFactory I get the SipStack class
3. I create a litening point (in the createListeningPoint() method I 
need to add the remote host or the local ip/port/transport?)
4. I create a SipProvider
5. I add sip listener class
And now? how can I call the first user?
I think I need to send a request (maybe I need a credentials for 
identify the current user?), I need to send a register command?
I think after that I create an RTP "port" and call the second host and 
if it's "connected" I send the rtp messages to each others...

Please help.

Thnx.
Cow...