https://bugs.openldap.org/show_bug.cgi?id=9839
--- Comment #2 from Howard Chu hyc@openldap.org --- Port=0 is meaningless for clients, so why would anyone ever run into this?
In #9596 it's done to allow slapd to listen on a dynamically assigned port. There is no use case for it anywhere else. It's also questionable whether the change for #9596 is actually appropriate.