The VTP system defines three types of nodes—Author, Broker and Subscriber—and two types of conenction—Author to Broker and Broker to Subscriber. Comet has the capability to act in all of these roles. To do so, it provides two different tools.

The first is comet-sendvo. This provides the capability of publishing a VOEvent packet to a remote broker. In other words, comet-sendvo assumes the role of Author in the above terminology, connects to a remote Broker, and delivers an event to it. The user invoking Comet in this mode is, of course, responsible for actually providing the event text to be sent.

The second tool is the Comet broker itself. This runs as a background process (daemon), and can:

  • Accept submissions from Authors (such as comet-sendvo);
  • Subscribe to streams of events from one or more remote Brokers;
  • Distribute events received (whether by direct author submission or by subscription) to its own subscribers;
  • Perform arbitrary actions upon events received.