[‘
In software terms, especially at the operating system level, a port is a logical construct that identifies a specific process/application or a type of network service and each network service running on a Linux system uses a particular protocol (the most common being the TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)) and a port number for communicating with other processes or services.
n
In this short article, we will show you how to list and monitor or watch running TCP and UDP ports in real-time with a socket summary on a Linux system.
n
List All Open Ports in Linux
n
To list all open ports on a Linux system, you can use the netstat command or ss utility as follows.
n
It is also crucial to mention that netstat command has been deprecated and instead ss command has taken its place in showing more detailed network statistics.
n
$ sudo netstat -tulpnrnORrn$ sudo ss -tulpnrn
n
n
From the output of the above command, the State column shows whether a port is in a listening state (LISTEN) or not.
n
In the above command, the flag:
n
- n
-t– enables listing of TCP ports.-u– enables listing of UDP ports.-l– prints only listening sockets.-n– shows the port number.-p– show process/program name.
n
n
n
n
n
n
Watch TCP and UDP Open Ports in Real-Time
n
However, to watch TCP and UDP ports in real-time, you can run the netstat or ss tool with the watch utility as shown.
n
$ sudo watch netstat -tulpnrnORrn$ sudo watch ss -tulpnrn
n
n
To exit, press Ctrl+C.
n
You will also find the following articles useful:
n
- n
- 3 Ways to Find Out Which Process Listening on a Particular Port
- How to Check Remote Ports are Reachable Using ‘nc’ Command
- How to List All Running Services Under Systemd in Linux
- 29 Practical Examples of Nmap Commands for Linux System/Network Administrators
n
n
n
n
n
That’s all for now! If you have any questions or thoughts to share about this topic, reach us via the comment section below.
n
‘]