[CalendarServer-users] Is an XMPP server required to get invites?

My install of the latest revision (5304) of CalendarServer works pretty well, except for the fact that I cannot RECEIVE any invitations in iCal. Does this require having an XMPP server, and configuring the caldavd.plist accordingly? Similarly, replies to invitations from my end are not received - and if I drag and drop a reply into iCal, I have seen some invitations (maybe all) are noted as "cancelled" by calendarserver, even though it has not actually been cancelled. Any ideas? -- Conrad Wasmer