You can use the port 1-65535, where 0- 1023 is a fixed port and is also a well-known port, such as Telnet (port number 23), FTP (port number 2 1), Http (port number 80) and so on. And 1024-65535 is a dynamic port!

(1) well-known ports

Well-known ports are well-known port numbers from 0 to 1023, which are generally assigned to some services. For example, port 2 1 is assigned to FTP service, port 25 is assigned to SMTP (Simple Mail Transfer Protocol) service, port 80 is assigned to HTTP service, port 135 is assigned to RPC (Remote Procedure Call) service and so on.

(2) Dynamic port.

Dynamic ports range from 1024 to 65535, and these port numbers are generally not fixed to a service, which means that many services can use these ports. As long as a running program requests the system to access the network, the system can assign one of these port numbers to the program. For example, port 1024 is assigned to the first program that sends an application to the system. After closing the program process, the occupied port number will be released.