How to get a list of open ports in Linux?

So you have set up a very secured server but still don't you want to cross check if the machine is really secured and your server has not been compromised by anyone. If is always better to regularly scan your system with open ports and list of connected machines.

For this blog I will show you the command to get a list of open ports in any machine

nmap command can be used to do the same. You can download in RedHat machine using yum
# yum install nmap
Once installed verify the package

# rpm -qa | grep nmap
nmap-5.51-2.el6.i686
Syntax
# nmap <address>

# nmap localhost
Starting Nmap 5.51 ( http://nmap.org ) at 2013-09-18 12:04 IST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.0000080s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 995 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
111/tcp open rpcbind
631/tcp open ipp
5989/tcp open wbem-https
Nmap done: 1 IP address (1 host up) scanned in 0.29 seconds

Here as you can see I got a long list of opened ports on my machine.

Go ahead and try the same on your machine.

Related Articles
What are the s and k scripts in the etc rcx.d directories
How to check all the currently running services in Linux
How to auto start service after reboot in Linux

Follow the below links for more tutorials:

Configure Red Hat Cluster using VMware, Quorum Disk, GFS2, Openfiler
Tutorial for Monitoring Tools SAR and KSAR with examples in Linux
How to configure Samba 4 Secondary Domain Controller
How to secure Apache web server in Linux using password (.htaccess)
How to register Red Hat Linux with RHN (Red Hat Network )
Red hat Enterprise Linux 5.5 Installation Guide (Screenshots)
15 tips to enhance security of your Linux machine
Why is Linux more secure than windows and any other OS
What is the difference between "su" and "su -" in Linux?
What is kernel-PAE in Linux?
What is swappiness and how do we change its value?
How to log iptables messages in different log file
What is virtual memory, paging and swap space?
Iptables rules to allow/block ssh incoming/outgoing connection in Linux
Iptables rules to block/allow icmp ping request in Linux