Use this tag for Ethernet ports. E.g. IP:port.
A device connected via Etheret tyipcally has at least one IP address, but needs to communicate with many different hosts/programs. To make a distiction between these a number is added, much akin to an internal extension number for phones.
These numbers range from 1 to 65536, with the lower 1024 often reserved by the host OS to indicate they programs listening on these ports are more trusted.
Many programs alway use the same port numbers for initial request, for a list of these see https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers