See what hosts on your LAN provide Universal Plug-and-Play (UPnP) and Simple Service Discovery Protocol (SSDP) services and where to find them. Taken from here.
# Listen for all UPnP broadcasts (including yourself).
# NOTE: 239.255.255.250 is a special multicast address that all IPv4 UPnP uses
sudo tcpdump -vv -A -s 0 'port 1900 and host 239.255.255.250 and udp'