Session Announcement Protocol. SAP is defined in RFC 2974. SAP broadcasts information to all devices on a well-known multicast address and port (using UDP). All devices listening to that port receive periodic information on available sessions. Essentially devices receive an updated ‘business card’ from any participating device from time to time.
SAP typically uses Session Description Protocol (SDP) as the format for Real-time Transport Protocol session descriptions.
Bonjour can be used to do a similar thing, but offer much greater functionality
See Bonjour
