The so-called port number is just like the house number. The client can find the corresponding server by ip address, but the server has many ports, and each application corresponds to a port number. Only through the port number similar to the house number can the client really access the server.

The main function of port number is to represent the service provided by a specific process in the computer.

Computers in the network represent their identities through IP addresses, which can only represent a specific computer, but a computer can provide many services at the same time, such as database services, FTP services, Web services and so on. We distinguish these different services provided by the same computer by port numbers.

For example, the common port number 2 1 means FTP service, port number 23 means Telnet service and port number 25 means SMTP service.

Extended data

Port protocol classification

1, TCP port

Transmission control protocol transmission control protocol. TCP is a connection-oriented, reliable and byte stream-based transport layer communication protocol, which is interpreted by RFC793 of IETF. In the simplified OSI model of computer network, it completes the functions specified by the fourth layer transport layer.

2.UDP port

User datagram protocol. UDP is a connectionless transport layer protocol in OSI reference model, which provides simple and unreliable information transmission service oriented to transactions. UDP protocol is basically the interface between IP protocol and upper layer protocol. UDP protocol is suitable for multiple applications running on the same device.