In this range, the ports below 1023 have been allocated to some common applications, and the ports after this number are used, so the ports available for network programming are generally selected after 1024.

In network technology, ports have two meanings:

1, ports in the physical sense, such as interfaces used by ADSL modems, hubs, switches and routers to connect other network devices, such as RJ-45 port and SC port;

2. Logically speaking, ports generally refer to ports in TCP/IP protocol, with port numbers ranging from 0 to 65535, such as port 80 for browsing web services, port 2 1 for FTP services, and so on.

Extended data

The actual purpose and port number of each port.

1 and 1 serial ports

The POP3 server opens the 102 port to receive mail, and the client accesses the mail service on the server side; News newsgroup transport protocol, carrying USENET communication. The connection of this port is usually that people are looking for a USENET server; 137 and 138 are UDP ports, which are used when transferring files through my online neighbors.

2, 2 serial ports

The FTP server opens port 2 1 for uploading and downloading. The most common attacker is to find a way to open anonymous's FTP server. These servers have read-write directories; The connection between TCP and port 22 established by PcAnywhere may be to find ssh；; The purpose of scanning port 23 is to find the operating system running on the machine.

Three 3-series ports

Lightweight Directory Access Protocol and port 389 of NetMeeting Internet Locator Server * * *.

Four 4-series ports

Web browsing port 443, another HTTP, which can provide encryption and transmission through a secure port; Trojan hacker paradise opens port 456.

Baidu encyclopedia-port number

Baidu encyclopedia-network port