Port number-the identification number of the application software with network function. Note that the port number is not fixed, that is, it can be assigned manually by the user (of course, it is usually defined when writing software). Of course, many applications recognize the default ports, such as FTP: 20 and 2 1, http: 80, telnet: 23 and so on. I won't list them here. A software can have multiple port numbers, which proves that the software has more than one network function.

0- 1023 is a recognized port number, that is, it has been recognized or reserved for the software to be recognized, while 1024-65535 is a port number that has not been defined by public * * *, and users can define the functions of these ports themselves.