To understand the meaning of ports, you need to know how the data in the network is packaged and unpacked. Through the understanding of data packaging and unpacking, we can truly understand and even feel the meaning of ports.
In addition, there are many tools to view ports, and the command line command netstat is commonly used. This command is the same in many operating systems and has many parameters. I usually use netstat -an.
The closing port can be set in the TCP/IP protocol of the operating system, or in the firewall of the operating system and third-party software (firewall, etc.). ).
You have a big problem, and there are a lot of related knowledge of connotation and extension worth learning.