IP address
An IP address serves two principal functions. It identifies the host, or more specifically its network interface, and it provides the location of the host in the network, and thus the capability of establishing a path to that host. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."
The header of each IP packet contains the IP address of the sending host, and that of the destination host.
Port (computer networking)
The Telnet service received the first official assignment of the value 1.
In detail, the first set of assignments was:
In the early ARPANET, the AEN was also called a "socket name", and was used with the Initial Connection Protocol (ICP), a component of the Network Control Program (NCP). NCP was the forerunner of the modern Internet protocols. Today the terminology "service name" is still closely connected with port numbers, the former being text strings used in some network functions to represent a numerical port number.