Expected response on ssdp:discover

[simoncn]

See this post for an explanation of why enabling multicast forwarding between the subnets is not sufficient.

The expected response to the M-SEARCH multicast message is a unicast UDP message sent to the source IP address and port that sent the M-SEARCH request to the multicast address. If you haven't set up routing between your subnets for unicast UDP messages, the media server's attempt to send this message will fail.