On a TCP/IP network every device must have an IP address. The IP address identifies the device e.g. computer. However an IP address alone is not sufficient for running network applications, as a computer can run multiple applications and/or services. Just as the IP address identifies the computer, The network port identifies the application or service running on the computer. The use of ports allow computers/devices to run multiple services/applications. The diagram below shows a computer to computer connection and identifies the IP addresses and ports.
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