Office Communicator ports


Does anybody have Microsoft Office Communicator working through a firewall
delivering voice, video and application sharing. I know Communicator is
built on the principle of Windows Messenger which works but communicator
will only enable me to do a one-way call. I have a DrayTek router and it
seems to work correctly. I've been through Google and opened the
recommended ports, I've even tried UPnP but get the same issue. I start
video connection or voice call, the other end can hear and see me but I get
nothing back. Router reports no error, I've even moved the workstation into
the routers DMZ and get the same this. Have considered the option that it
could be the other end, if they initiate the session it works OK and two-way
comms is possible.

Don't have any issues with NetMeeting or MSN Messenger. And workstation
firewall doesn't seem to make a difference.

Please let me know if you have it working and what ports are open.