Details of Linux forced release of occupied ports and Linux firewall port opening methods

When installing nginx, mysql, tomcat, and so on, you may encounter a problem where the port you need to use is somehow occupied. Here's how to solve this problem.

When it comes to ports, I have to mention firewalls, and this article briefly describes how to configure firewall development ports.

Various ways for Linux to view port conditions

The mapping relationships for all ports are in the /etc/services file

The port number of Linux is from 0 to 65536. The purpose of each port number is as follows:

0-1023: Recognized ports, bound to common services (FTP, SSH)

1024-49151: Register ports for binding to 1 or more services

49152-65535: Dynamic or private port, available for any network connection

Ports are divided into TCP and UDP transport protocols.

Linux view port status command

The following commands can be used to view the port situation. Click the command to adjust the usage details of each command:

nmap Command, port scan used

netstat Detection development port

lsof Check the port descriptor

#  View the port that binds the native 
nmap 127.0.0.1

#  check 3306 port 
netstat -anlp | grep 3306

#  detection 3306 interface 
lsof -i:3306

linux release the occupied port solution

The solution steps are as follows:

Find the process occupying the port

Kill the process

Just use the following command:

# can be written as 1 command

netstat -anp|grep 8080|awk '{print $7}'|awk -F '/' '{print $1}'|xargs kill -s 9

The meanings of the commands are as follows:

netstat -anp Displays all network usage and shows the usage program

grep 8080 Records matching port 8080 (may contain 18080)

awk '{print $7}' Output the process in column 7 as follows: 18989/nginx

awk -F '/' '{print $1}' Intercepting process PID: 18989

xargs kill -s 9 Kill the process using the output of the previous command as an argument

Release the occupied port as a step by step solution

Query whether the port is occupied

For example, if you need to check whether port 8080 is occupied, you can use the following command

netstat -an | grep 8080

Query the process occupying the port

You can view it using the lsof command

lsof -i:8080

You can also view it using netstat and grep

netstat0

The last line of this command is the process PID and its name occupying port 8080.

Kill the process occupying the port

You can use the kill command to directly kill the process you found in the previous step.

kill -9 19664

linux firewall release port

Linux Firewall up and down

The firewall described below is iptable and does not apply to firewalld.

Firewall enabled (permanent after restart) : chkconfig iptables on
Firewall turned off (permanent on restart) : chkconfig iptables off
Firewall on (effective immediately, expired after restart) : service iptables start
Close firewall (effective immediately, expired after restart) : service iptables stop
Restart firewall :service iptables restart

Linux to view firewall status

You can use the following command to see:

/etc/init.d/iptables status

#  Or abbreviations 
iptables status
iptables -L

#  You can also view the configuration file directly 
vim /etc/sysconfig/iptables 

Linux opens a port on the firewall

For example, open port 8080, you can use the following command:

iptables -A INPUT -p tcp --dport 8080 -j ACCEPT
#  You also need to restart the service 
service iptables restart

#  You can also edit configuration files directly 
vim /etc/sysconfig/iptables
#  Then add it at the end of the file 1 Okay, let's develop 8080-8181 Between all ports 
iptables -A INPUT -p tcp --dport 8080:8181 -j ACCEPT

Among them

�A The argument is just like adding 1 rule
�p What protocol is it, the tcp protocol that we use, and of course udp
�dport Is the target port, when data from the outside into the server for the target port
�sport When the data goes out of the server, it is used for the data source port
�j Specify ACCEPT - to receive or DROP not to receive

The above is about Linux forced release and Linux firewall port opening methods. To see more articles on Linux ports, click on the related article below