PortPeeker

Have you ever wanted to figure out which ports are open on a particular server? Do you own or administer a large number of machines and need a way to check them for open ports? If so, PortPeeker is just what you're looking for. PortPeeker is an extremely flexible and fast portscanning script. You can scan a single host or a range of contiguous IP addresses, and you can scan each host for a single port, a range of ports, or a list of specific ports you determine.