"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.

Port type:

TCP port and UDP port. Because TCP and UDP are independent, their respective port numbers are also independent of each other. For example, TCP has 235 ports, and UDP can also have 235 ports. There is no conflict between them.

1. well-known port

Well-known ports are well-known port numbers ranging from 0 to 1023, of which 80 ports are allocated to WWW service and 2 1 ports are allocated to FTP service. We don't need to specify the port number when we enter the URL in the address bar of IE, because by default, the port of WWW service is "80".

Network services can use other port numbers. If it is not the default port number, you should specify the port number in the address bar by adding a colon ":"(half angle) after the address and then adding the port number. For example, if you use "8080" as the port of WWW service, you need to enter "URL: 8080" in the address bar.

However, some system protocols use fixed port numbers and cannot be changed. For example, port 139 is specially used for communication between NetBIOS and TCP/IP and cannot be changed manually.

2. Dynamic port

The range of dynamic ports is from 49 152 to 65535. It is called a dynamic port because it generally does not allocate a service fixedly, but dynamically.

3. Register the port

Ports 1024 to 49 15 1 are assigned to user processes or applications. These processes are mainly applications that some users choose to install, rather than common programs that are assigned recognizable ports. When these ports are not occupied by server resources, clients can dynamically select them as source ports.