NMap

Nmap features include:

• Host Discovery - Identifying computers on a network, for example listing the computers which respond to pings, or which have a particular port open
• Port Scanning - Enumerating the open ports on one or more target computers
• Version Detection - Interrogating listening network services listening on remote computers to determine the application name and version number
• OS Detection - Remotely determining the operating system and some hardware characteristics of network devices.

DOWNLOAD SITE : http://nmap.org/download.html , insecure.org