From OpenHome
Songcast OHM/OHU Protocol Specification (Version 1.0)
Introduction
OHM, OHU, together with OHZ (discussed separately here), form a family of OpenHome protocols for the transport of 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.
Message Format
The OHM and OHU protocols share the same message format.