Sonos is (or was) mostly UPnP with some extensions... so for discovery they used SSDP https://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol https://en

Sonos is (or was) mostly UPnP with some extensions... so for discovery they used SSDP https://en.wikipedia.org/wiki/Simple_Service_Discovery_Protocol https://en.wikipedia.org/wiki/Simple_Service_Discovery_Proto.... I messed around with their stack and internals for a while about ten years ago... some remnants remain https://github.com/NathanHowell/Sonority/tree/master/ https://github.com/NathanHowell/Sonority/tree/master/ https://github.com/NathanHowell/Sonority/tree/core/ https://github.com/NathanHowell/Sonority/tree/core/ https://github.com/NathanHowell/upd2 https://github.com/NathanHowell/upd2