The multicast discovery agent uses the IP multicast protocol to find any message brokers currently active on the local network. The agent requires that each broker you want to advertise is configured to use the multicast agent to publish its details to a multicast group. Clients using the multicast agent as part of the discovery URI they use for connecting to a broker will use the agent to receive the list of available brokers advertising in the specified multicast group.

The multicast discovery agent URI conforms to the syntax in Example 7.

multicast://GroupID

Where GroupID is an alphanumeric identifier. All participants in the same discovery network must use the same GroupID.

For a broker to be discoverable using the multicast discovery agent, you must enable the discovery agent in the broker's configuration. To enable the multicast discovery agent you set the transportConnector element's discoveryUri attribute to a mulitcast discovery agent URI as shown in Example 8.

<transportConnectors>
  <transportConnector name="openwire"
    uri="tcp://localhost:61716"
    discoveryUri="multicast://default" />
</transportConnectors>

The broker configured in Example 8 is discoverable as part of the multicast group default.

To use the agent a client must be configured to connect to a broker using a discovery protocol that uses a multicast agent URI as shown in Example 9.

discovery://(multicast://default)

A client using the URL in Example 9 will discover all the brokers advertised in the default multicast group and generate a list of brokers to which it can connect.