Linux checks all ports open to the outside world

Linux checks all ports open to the outside world

Centos 8 view all ports open to the outside world

查看防火墙对对应的端口是否已开启
firewall-cmd --list-all

way 1

The port used by the known service to see if the service is listening

netstat -anlp | grep 3306

way two

Query the ports that all services listen on

Install the nmap tool to detect open ports

1. Download the installation package

http://nmap.org/dist/nmap-7.01.tar.bz2

2. Unzip

tar -xvf nmap-7.01.tar.bz2 

3. Enter the directory to execute

cd /nmap-7.12
./configure

若报错“configure: error: no acceptable C compiler found in $PATH”，
说明未安装gcc，gcc安装命令为#yum install gcc. 
执行#make 若报错“-bash: make: command not found”，
则执行#yum install g++或#yum install gcc-c++安装gcc。 

4、make

5、make install

6. Check whether the installation is successful

nmap -v

After installing the nmap tool, you can use the tool to query the port that is open to the outside world and listen to the service

implement:nmap 127.0.0.1

Starting Nmap 7.01 ( https://nmap.org ) at 2022-10-10 17:39 CST
Warning: File ./nmap-services exists, but Nmap is using /usr/local/bin/../share/nmap/nmap-services for security and consistency reasons.  set NMAPDIR=. to give priority to files in your local directory (may affect the other data files too).
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000010s latency).
Not shown: 998 closed ports
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http