The network port mainly identifies the processes running on the host (the processes here can understand some software), and each process has its own port number. For example, the ip of host A is 192. 168. 1, the ip of host B is192.1.2, and the ip of host C is1. Now host A needs to send information to host C. First, it will distinguish whether the host to be sent is C by ip address. After determining the host, you also need to determine which process in host C the message is sent to. Processes are distinguished by port numbers.

According to TCP/IP protocol, a computer has 65,536 ports, which can be divided into TCP ports and UDP ports. If divided by port number, it can be divided into the following two categories:?

System reserved port (from 0 to 1023). These ports are not allowed to be used by customers themselves, and they all have exact definitions, which correspond to some common services on the Internet. Each open port represents a system service, for example, port 80 represents a Web service. ?

Dynamic port (from 1024 to 65535). When customers need to communicate with others, Windows will assign a dynamic port on this computer from 1024. If the port is not closed, when the port is needed again, it will allocate 1025 for you to use, and so on. However, individual system services will be bound to ports 1024 to 49 15 1, such as port 3389 (Remote Terminal Service). From 49 152 to 65535, there is usually no bundled system service, allowing Windows to dynamically allocate to customers.

Supplement: Commonly used port numbers

21:The port opened by FTP service is used for uploading and downloading files.

22: SSH port, which is used to remotely connect Linux server or vps through command line.

23: Telnet port, used to telnet to the server.

25: Port opened by SMTP service for sending mail.

80: HTTP is used for HTTP service to provide access function.