I have a firewall that separates my wired LAN subnet where my SmartThings Hub is connected and my Sonos speakers which sit on the WiFi subnet.
I was able to successfully forward broadcast and multicast traffoc through the firewall (FortiGate) by changing configuration settings. I confirmed this by running a tcpdump on a Linux device which I have on the wired network. I confirmed that I see SSDP packets (UDP 1900) coming into that device via the broadcast address (255.255.255.255). I did a full packet trace and see the XML file indicating the HTTP URL to connect to the Sonos speaker.
When I try and add ‘things’ from my SmartThings app nothing is discovered. The Logs on my hub say ‘In ssdpDiscover’ followed by ‘No devices to add, verified devices: [:]’
I turned logging on my firewall and also ran a network trace on the wired subnet of the firewall interface. All packets from SmartThings are being accepted and forwarded but the only traffic I see from SmartThings is UDP traffic to the Sonos IP on port 9. The packet reaches the Sonos device but it just responds with ‘port 9 is unreachable’.
Long story shot, looks like everything is being forwarded properly – I really think this should work. Anyone have more info on how SmartThings goes about its discovery process?