Nmap is a utility for network exploration or security auditing. It
supports ping scanning (determine which hosts are up), many port
scanning techniques, version detection (determine service protocols
and application versions listening behind ports), and TCP/IP
fingerprinting (remote host OS or device identification). Nmap also
offers flexible target and port specification, decoy/stealth scanning,
sunRPC scanning, and more. Most Unix and Windows platforms are
supported in both GUI and commandline modes. Several popular handheld
devices are also supported, including the Sharp Zaurus and the iPAQ.