What ports need to be open for Calendar and Contacts services to facilitate calendar resources on Mac OSX Server 10.8

Question

We use Mac OSX 10.8 with Server 2.2.1.

When creating a calendar appointment on a client connected to the OSX server from within our local network (behind our firewall) we can select calendar resources and view other's availability. Outside our network, and in front of our firewall, this function does not work.

We currently have ports 389 and 636 (LDAP/SSL) as well as 8008 and 8443 (Calendaring/SSL).

My gut is telling me that Bonjour might be helping out when inside our network.

Answer 1

What I've learned so far:

• In order to facilitate a CalDav service to the outside world, forwarding port 8008 and 8443 sufficed for me.
• However, in order to allow users to add an Internet Account via System Preferences, port 443 needs to be accessible as well. Authentication and selecting which services are to be used is done over port 443.

This is not a complete solution yet, though, as I'm now stuck at a 'critical error' when creating an iCal agenda in the newly created account:

To be continued.

Note: my issue is nearly identical to the question at hand, and I'll be tracking my progress here when it is no longer relevant to this specific question.