How to Check Open TCP/IP Ports in Windows
linux - Check the Number of active connections on port 80 This will show all connections to the local ports 80 or 443 (add/modify port(s) if needed). Disclaimer: I realize this is an old question, but it's still the top result at Google, so I … 2.2.9. Verifying Which Ports Are Listening Red Hat Use the -6 option for scanning an IPv6 address. See man nmap(1) for more information. The following is an example of the command to be issued from the console of another system to determine which ports are listening for TCP connections from the network:
How to: Check/View ports in use/listening ports locally on
Jun 26, 2019 How To Check List Of Open Ports In Linux | 2daygeek.com Sep 13, 2019 Open ports in Ubuntu • Linux Hub
If you are looking for continuous monitoring of ports for server machines or local I think you can also use graphical version of nmap i.e Zenmap for more detailed version. Zenmap is the official graphical user interface (GUI) for the Nmap Security Scanner. Supports available (Linux, Windows, Mac OS X, BSD, etc.) Have a look to this tool view:
Mar 31, 2019 Question: How To See What Ports Are Open Linux? - OS Today