Voice connection problem

[David Griffiths]

I am trying to connect with a live conversation....
Neither I nor my partner could establish a connection
until I disabled my firewall, and then she could hear me,
but no voice came from her end. Does she need to disable
her firewall as well, or is there a work-around so that we
can keep firewalls in place? Some port settings need to
be changed?? How, where???

Thanks,

David in Seattle trying to reach Valerie in England.