Nmap (Network Mapper) is a security scanner used to discover hosts and services on a computer network, thus building a "map" of the network. It is designed to scan large networks rapidly, 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. It is highly flexible, allowing for a wide range of advanced techniques, such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. Therefore, for the reconnaissance purposes described in the question, Nmap is the appropriate tool for Martin to employ.