Tutorial on using Netstat to Check for Open TCP / UDP Ports in Linux. Netstat tends to come pre-installed in Linux, you can use it for setting up firewall rules and fault finding on Linux Clients and Servers. A similar command exists in Windows, but uses different arguments.

netstat -natup

(Numeric, All, TCP, UDP, Show PID) ... https://www.youtube.com/watch?v=Lcw9bTW06cs