Building a CalDAV client

Building a CalDAV client involves service discovery, authentication, and implementing the CalDAV protocol operations.

Steps

1. Service Discovery

Locate the user’s CalDAV server:

1. Try /.well-known/caldav on the user’s server domain.
2. Follow HTTP redirects to the actual CalDAV endpoint.
3. Optionally check DNS SRV records (_caldav._tcp.domain).

2. Principal Discovery

PROPFIND the well-known URL to find the user’s principal URL:

<D:propfind xmlns:D="DAV:">
  <D:prop>
    <D:current-user-principal/>
  </D:prop>
</D:propfind>

3. Calendar Home Set

PROPFIND the principal URL to get the calendar home set:

<D:propfind xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:caldav">
  <D:prop>
    <C:calendar-home-set/>
  </D:prop>
</D:propfind>

4. List Calendars

PROPFIND the calendar home set to list available calendars.

5. Query Events

Use calendar-query REPORT to fetch events by time range.

6. Create/Update Events

PUT an iCalendar resource to a URL within a calendar collection.

7. Synchronize

Use sync-collection REPORT with a sync token for efficient incremental updates.