How to close the linux port?

How to close the Linux port? The following article will introduce to you how to check whether the port is open, close/open the port under Linux. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

1. Check which ports are open

netstat -anp

(Note: Adding parameter '-n' will convert the application to port display, that is, digital format address, such as: nfs->2049, ftp->21, so you can open two terminals and correspond to the port number corresponding to the program one by one)

2. Close the port number

iptables -A OUTPUT -p tcp --dport 端口号-j DROP

3. Open the port number:

iptables -A INPUT -ptcp --dport  端口号-j ACCEPT

4. Save the settings

service iptables save

5. The following is how to use the Linux open port command.

nc -lp 23 &(打开23端口，即telnet)
netstat -an | grep 23 (查看是否打开23端口)

6. Linux open port command Each open port needs a corresponding listening program

Recommendation: "linux tutorial"

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