Network port number

I. Network port

In network technology, Port includes two types: logical port and physical port.

Physical ports refer to physically existing ports, such as interfaces used to connect other network devices on hubs, switches, and routers.

Logical port refers to the port used to differentiate services logically, such as the service port in TCP/IP protocol (16 bits), the range of port number [0,65535], such as port 80 for browsing web services, port 21 for FTP services, and so on.

Because of the large number of physical and logical ports, each port is numbered in order to distinguish the ports, which is the port number. The port number only has a local meaning, only to mark the interlayer interface of each process in the application layer of the computer when interacting with the transport layer.

II. Port number layout and classification

1. The port number used on the server side:

(1) be familiar with the port number / system port number, and the value is [0room1023]. IANA assigns these port numbers to some of TCP/IP 's most important applications to make them well known. Whenever a new application appears, IANA must assign it a familiar port, otherwise it will not be able to communicate.

Application FTPTELNETSMTPDNSTFTPHTTPSNMPSNMP (trap) knows the port number 212325536980161162 Table 1: commonly known port number

(2) Registration port number: the value [1024049151] is used by applications that are not familiar with the port number. The use of this type of port number must be registered at IANA in accordance with the prescribed procedures to prevent duplication.

2. The port number used by the client:

The numeric value [49152 / 65535], also known as "short port number" (this type of port number is dynamically selected only when the client process is running). This type of port number is left to the client process to choose to use temporarily.