Supplement:
"port" is a free translation of English port, which can be considered as the exit of communication between equipment and the outside world. Ports can be divided into virtual ports and physical ports, where virtual ports refer to the ports inside the computer or in the switch router and are invisible. Such as port 80, port 2 1, port 23, etc. Physical ports, also known as interfaces, are visible ports, RJ45 network ports on the computer backplane and RJ45 ports, such as switch router hubs. Phones using RJ 1 1 jack also belong to the category of physical ports.
The system program that the computer runs is actually like a closed circle, but the computer serves people, and he needs to accept some instructions and adjust the system function according to the instructions to work. So the system programmer cut the circle into many segments, and these line segment interfaces are called ports (in layman's terms, breaks, that is, interrupts). When the system runs to these ports, it is necessary to check whether these ports are open or closed. If they are closed, the rope is connected and the system runs downward.
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