What LDAP port?

I have upgraded our NT 4.0 server to Win 2k and am attempting to complete an upgrade of our Exchange 5.5 to 2k. I understand that the active directory uses the port 389 which is the same one that Exchange uses. I am running Terminal services on this server for remote administration. So I would like to know What port I should use? I tryed 589 but when I try to connect to Exchange it tells me that The Exchange 5.5 Directory service could not be contacted please ensure it is listening on the correct port.