For example, if the server is a bank, then the port is its counter, and the service of each port is different (the service of each counter of the corresponding bank is also different). Some counters handle cash deposits and withdrawals, some handle inter-bank transfers, some handle wire transfers, and some handle safes. The corresponding ports use service protocol, some ports use FTP protocol (downloading and uploading files), some ports are used for Http (browsing web pages), some ports are SMTP (sending mail), some ports are POP3 (receiving mail) and so on.

And the number of ports 1 * * * ranges from 0 to 65,534 * * with a total of 65,535 (service counters). The first 65,438+0024 is the default service of Windows operating system, and users or other applications can open it from port 65,438+0025. In other words, one port corresponds to one service. In addition, a port can be understood as a service window of an operating system or an application.