Click "Start → Run" in turn, enter "cmd" and press enter to open the command prompt window. Type "netstat -a -n" at the command prompt, and then press Enter to view the port number and status of TCP and UDP connections displayed in digital form.
Close/open port
Before introducing the functions of various ports, let's introduce how to close/open ports in Windows, because by default, many unsafe or useless ports are open, such as port 23 for Telnet service, port 2 1 for FTP service, port 25 for SMTP service, port 135 for RPC service and so on. In order to ensure the security of the system, we can close/open the port by the following methods.
Close the port
For example, to close port 25 of SMTP service in Windows 2000/XP, you can do this: first open the control panel, double-click the administrative tools, and then double-click the service. Then find and double-click the Simple Mail Transfer Protocol (SMTP) service in the opened service window, click the Stop button to stop the service, then select Disable in the Startup Type, and finally click the OK button. In this way, closing the SMTP service is equivalent to closing the corresponding port.
port
If you want to open the port, just select Automatic in the startup type, click OK, then open the service, click Start Enable Port in the service status, and finally click OK.
Tip: There is no "service" option in Windows 98. You can use the rule setting function of the firewall to close/open the port.
Port classification
Right-click My Computer-Properties-Remote-check Allow remote assistance invitation from this computer and allow users to connect to this computer remotely.
It is dangerous to open port 3389. Don't mess with hackers and get burned.