Over the last two weeks we’ve worked with the Server app on macOS Sierra to set up the Calendar service. The Calendar service uses CalDAV, a web standard that allows you to connect to calendar services, add and update events using a variety of calendar apps. In fact, when we were working with the calendar service you could have just as easily added your server’s calendar service to Fantastical or BusyCal because both support the CalDAV standard.
Server’s Contacts service works using a similar standard called CardDAV, which, like CalDAV, allows a variety of contact apps to connect to and update data stored on your server. And, in fact, CalDAV and CardDAV are linked to each other on your server. You can see this link using the Server apps log tools.