Web Services Dynamic Discovery (WS-Discovery) (2005)

This specification defines a multicast discovery protocol to locate services. The primary mode of discovery is a client searching for one or more target services. To find a target service by the type of the target service, a scope in which the target service resides, or both, a client sends a probe message to a multicast group; target services that match the probe send a response directly to the client. To locate a target service by name, a client sends a resolution request message to the same multicast group, and again, the target service that matches sends a response directly to the client. To minimize the need for polling, when a target service joins the network, it sends an announcement message to the same multicast group. By listening to this multicast group, clients can detect newly-available target services without repeated probing. [via]

http://specs.xmlsoap.org/ws/2005/04/discovery...