For any system administrator, it is crucial to monitor the open ports in your Linux system to ensure a robust and secure environment. By knowing which ports are open, you can verify if necessary applications are running correctly, or if any unwanted applications are consuming your system’s resources.
In this post, we’re going to learn about various commands that you can use to view open ports in Linux.
1. The Netstat Command
The netstat (Network Statistics) command is a versatile tool that provides information about the network connections, routing tables, interface statistics, and more. It is widely used to monitor network traffic.
To list all the open ports using netstat, you can use the command below:
netstat -lntu
The flags used in this command are -l (that shows all listening sockets), -n (that shows numerical addresses instead of trying to determine symbolic host names), -t (for TCP ports), -u (for UDP ports).
2. The lsof Command
lsof (List of Open Files) is another powerful command which is used not only to list open files but also to find out which files are opened by which process.
To use this command to list all open ports, use:
lsof -i
You can also filter the results for a specific port using the command:
lsof -i :<port_number>
3. The ss Command
Another useful command is ss (Socket Statistics), which is used to dump socket statistics and displays information similar to netstat.
To view all open ports using the ss command, use:
ss -lntu
The flags used here are the same as those used in the netstat command.
With these simple commands, you can ensure that your system is secure by monitoring the open ports and the applications using them. Remember, it is always crucial to make sure that only necessary ports are open to avoid any potential security breaches.
