If your not familiar with this by now, you should be.
Introducing, Nmap Network Scanner from -Insecure.org, test network security, vulnerabilities, and a whole lot more! Nmap was written by Gordon Lyon, also known in cyberspace as "Fyodor".
Gordon, also runs a few other websites s Insecure.Org, Nmap.Org, SecLists.Org, and SecTools.Org. Check them out. It will be worth the effort!
There are a whole list of free tools available at insecure.org. As well as a heap of free downloads, installation guides, docs, and more!