How to make to know to asterisk at what softphone must call

Hello, i need some help from you, I have installed the xlite phone in two computers (linux and windows), when I call from the windows Pc to the linux’s PC(server), the call is made correctly, but If I try to call from the server to the other PC, I cant, my question is How I must do to asterisk calls some specific phone in my network, I hope to have been very specif, if I wasnt, I’m sorry but I’m new in asterisk,

In advance, thanks

try setting

defaultip=

for each user in your sip.conf file

if you still cant connect you may have firewall issues.

thanks, i will try your suggestion