Keep an Eye on Your Linux Systems with Netstat
Two of the fundamental aspects of Linux system security and troubleshooting are knowing what services are running, and what connections and services are available. We're all familiar with ps for viewing active services. netstat goes a couple of steps further, and displays all available connections, services, and their status.
It shows one type of service that ps does not: services run from inetd or xinetd, because inetd/xinetd start them up on demand.
