Linux View port usage status, shutdown port method

First you must know that the port does not exist independently, it is dependent on the process. When a process is turned on, its corresponding port is turned on and the process shuts down, and the port is closed. The next time a process is turned on again, the corresponding port is turned on again. Instead of purely understanding that a port is closed, you can disable a port.

1. You can use

Netstat-anp

To see which ports are open.
(Note: The parameter '-n ' will convert the application to port display, that is, the address of the number format, such as: nfs->2049, ftp->21, so you can open two terminals, one for each corresponding to the port number of the program)

2. You can then pass

Lsof-i: $PORT

Check the program that applies the port ($PORT refers to the corresponding port number) or you can view the file/etc/services, from which you can find the service that corresponds to the port.

3. To close a port, you can:
1) Disable the port via the Iptables tool, such as:

sudo iptables-a input-p tcp--dport $PORT-j dropsudo iptables-a output-p tcp--dport $PORT-j DROP

　　

2) or turn off the corresponding application, the port will naturally shut down, such as:

Kill-9 PID (PID: Process number)

such as: Through

NETSTAT-ANP | grep ssh

have shown:

TCP 0 127.0.0.1:2121 0.0.0.0:* LISTEN 7546/ssh

The

Kill-9 7546

("~$ chkconfig" can be used to view the open state of the system service.)

Linux View port usage status, shutdown port method