[Serusers] How to make SER keep states

[M@rcio]

Hi,
I'm working with SER and I'm trying to make a state machine for SER. I'm
having some difficults on trying to understand how modules work, because
SER have to be extended to enable such functionality. The idea is to SER
recognize that a client has already estabilished a conection with a
video server throught SER's proxy and therefore SER must redirect the
new INVITE to another proxy. In this new proxy the trafic will be
multicast, so that everyone who wants the same video service will have
it.
SER  just need to recognize that two or more clients wants to estabilish
conection with the same terminal.
Can you help me in how or where in the modular arquitecture of SER will
I have to act?
Thanks.