In my Mac(192.168.2.228), it will send ICMP packet to my house's router (192.168.2.1).
with the info Destination unreachable (Port unreachable)
and in the Wireshark packet detail panel, there displays the packet structure:
eth:ehtertype:ip:icmp:ip:udp
and more details:
the payload is IP:UDP
(from router to mac), and you see the router port is 53
, it related to DNS.
and in my macOS, there is no application listening the port:
$ netstat -an | grep 55166
get nothing.
What's the protocol use the packet? and what's the intension of the packet?