Linux find out which port is open using the command line

You can use the lsof command to find out which ports are open on a Linux system:

This will display a list of all open Internet sockets and the processes that have opened them. The -i option is used to specify that you only want to display information about Internet sockets.

You can also filter the output to only display information about a specific protocol or port number. For example, to only display information about open TCP ports:

To only display information about a specific port number, such as 80 (HTTP):

Note that the lsof command requires root privileges to run, so you may need to run it using sudo.