From OpenHome
Songcast OHM/OHU Protocol Specification (Version 1.0)
Introduction
OHM and OHU, together with OHZ, form the Songcast family of OpenHome protocols for transporting audio around a home network.
- OHM provides large scale one to many communication using multicast UDP.
- OHU provides small scale one to many communication using unicast UDP.
OHU can be used to deliver Songcast functionality to networks that do not have proper multicast support.
Message Format
The OHM and OHU protocols share the same message format.