Call from computer to computer

hi ,

i am very new to this env.

can anyone help me out…

i have to just make an java application which makes call from computer to computer…

so plz…say what are the api i should use and openfire administration settings also…

do i need to give sip seetings also or is it enough for asterisk-im…

i am using openfire 3.6.3 and spark as a client.