[Evolution-hackers] How evolution commandline attachs to a running process of evolution?

[Joey Shen <joey shen sun com>]

Hi hackers,
I notice that if I launch the commandline, e.g. "evolution-1.3 mailto 
URL", when there is already a running process of evolution, the newly 
launched composer would attach to the running process. Could anyone tell 
me how evolution commandline achieve this? And where I can find the 
source code to deal with such kind of things?
Thanks a lot!
-JoeyS