Nmap - Nmap ("Network Mapper") is the free and open resource (license) utility for system exploration or security auditing. Many systems and system administrators also find this useful for tasks like network inventory, managing support upgrade schedules, and supervising host or service uptime. Nmap uses raw IP packets in novel methods to determine what hosts are usually available around the network, exactly what services (application name plus version) those hosts are usually offering, what operating systems (and OS versions) they may be operating, what type of box filters/firewalls are in make use of, and a large number of other features. It was made to swiftly scan large networks, nevertheless works fine against individual hosts.