foreword
When using linux, we often need to check whether the port is open. Here is how to check it.
1. Open port process
1.1 View firewall status
firewall-cmd --state
The state here is that the firewall is not closed, if it is running, it is in the running state.
1.2. Open ports
firewall-cmd --zone=public --add-port=6123/tcp --permanent
The open port here is port 6123, and you only need to change it to other ports to open other ports.
1.3. Reload
firewall-cmd --reload
1.4 Check if the port is open
netstat -aptn |grep 6123
After the port is opened, execute this command on the local machine, and you can see which program opened the port. For example, here is the port 24973, which is the java process.
Or other machines can execute the telnet command to check whether it is open.
For example, if I telnet this machine from other machines that communicate with each other in the network, I will get the following prompt, which means the opening is successful.
telnet 192.168.184.129 6123
Summarize
Open port means that the port needs to be opened only when the firewall is open. If the firewall is closed, there is no need to open the port. If you need to open or close the firewall, execute the following command
systemctl start firewalld.service
systemctl stop firewalld.service
If you need to boot, turn on and off the firewall and execute the following command
systemctl disable firewalld.service 开机关闭防火墙
systemctl enable firewalld.service 开机启动防火墙