some day I will run out of these
nmap
Nmap ("Network Mapper") is an open source utility for network exploration or
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 (ports)
they are offering, what operating system (and OS version) they are running,
what type of packet filters/firewalls are in use, and dozens of other
characteristics. Nmap runs on most types of computers, and both console and
graphical versions are available. Nmap is free software, available with full
source code under the terms of the GNU GPL
www.insecure.com/nmap
