There are three categories of ports in a Linux system:
Well-known ports: These are the ports that are reserved for specific services and are assigned by the Internet Assigned Numbers Authority (IANA). Some examples of well-known ports are 22 for SSH, 80 for HTTP, and 443 for HTTPS. Registered ports: These are the ports that are registered with the IANA for specific purposes but are not reserved for specific services. These ports are typically used by specific applications or protocols. Dynamic and/or private ports: These are the ports that are not reserved or registered with the IANA and can be used by any application or protocol. These ports are typically used for temporary or ephemeral connections.
In this article, we will cover several methods for checking open ports in Linux.
How to Check Open Ports in Linux
To check open or listening ports in Linux, you can use the netstat, ss, lsof, and nmap commands.
Conclusion
In this article, we covered several methods for checking open ports in Linux. We covered using the netstat, ss, lsof, and nmap commands to display a list of open ports and the corresponding processes. By using these methods, you can easily check open ports on your Linux system.
Open a terminal window and run the following command:
The -t flag displays TCP connections, the -u flag displays UDP connections, the -l flag displays listening sockets, the -p flag displays the PID and name of the process, and the -n flag displays numerical addresses instead of symbolic names.
The output of the command will show a list of open ports and the corresponding processes.
Open a terminal window and run the following command:
The -i flag specifies the Internet address of a file.
The output of the command will show a list of open ports and the corresponding processes.
You can also check for the speicifc port number:
Open a terminal window and run the following command:
The -t flag displays TCP connections, the -u flag displays UDP connections, the -l flag displays listening sockets, the -p flag displays the PID and name of the process, and the -n flag displays numerical addresses instead of symbolic names.
The output of the command will show a list of open ports and the corresponding processes.
Open a terminal window and run the following command:
The -p- flag specifies a range of ports to scan. The - indicates that all ports should be scanned.
The localhost argument specifies the target host to scan.
The output of the command will show a list of open ports on the target host.
I hope this helps you understand how to check open ports in Linux. If you have any further questions, please don’t hesitate to ask.
