угу, а дальше ман почитать?

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DESCRIPTION
Nmap (“Network Mapper”) is an open source tool for network exploration
and security auditing. It was designed to rapidly scan large networks,
although it works fine against single hosts. Nmap uses raw IP packets
in novel ways to determine what hosts are available on the network,
what services (application name and version) those hosts are offering,
what operating systems (and OS versions) they are running, what type of
packet filters/firewalls are in use, and dozens of other
characteristics. While Nmap is commonly used for security audits, many
systems and network administrators find it useful for routine tasks
such as network inventory, managing service upgrade schedules, and
monitoring host or service uptime.
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