title: avahi: broadcast that my service has updated information
body: <p>I have an avahi (zeroconf, dnssd, bonjour) service. I want the service to be able to notify the clients when it has new data so the clients can then connect and query for the updated information.</p>
  
  <p>What type of message should the service publish, and how is this done with the avahi API (service is written in C++)?</p>