(Zz) how to check the port usage status and disable the port in Linux

1. you can use ~ $ Netstat-anp to check which ports are opened. (Note: adding parameter-n will convert the application to Port display, that is, address in digital format, such as: nfs-2049, ftp-21, so you can enable two terminals, 1 corresponds to the port number corresponding to the program) 2. then you can use ~ $ Lsof-I: $ PORT "~ $ Netstat-anp "to check which ports are opened.
(Note: adding the '-n' parameter will convert the application into a port display, that is, a digital address, such as nfs-> 2049, ftp-> 21, therefore, you can enable two terminals to correspond one by one to the corresponding port number of the program)
2. then you can use "~ $ Lsof-I: $ PORT "to view the program that applies this PORT ($ PORT indicates the corresponding PORT number ). You can also view the/etc/services file to find the service corresponding to the port.
(Note: Some ports cannot be found through netstat. the more reliable method is "~ $ Sudonmap-sT-Olocalhost ")
3. to close a port, you can:
1) pass IptablesTool to disable this port, such:
"~ $ Sudoiptables-AINPUT-ptcp -- dport $ PORT-jDROP"
"~ $ Sudoiptables-AOUTPUT-ptcp -- dport $ PORT-jDROP"
2) or shut down the corresponding application, the port is closed, for example:
"~ $ Kill-9PID "(PID: Process ID)
For example "~ $ Netstat-anp | grepssh"
Display: tcp0127.0.0.1: 21210.0.0.0: * LISTEN7546/ssh
Then :"~ $ Kill-97546"

(You can use "~ $ Chkconfig "view the activation status of system services)