Port Scanner :

A port scanner is a piece of software designed to search a network host for open ports. This is often used by administrators to check the security of their networks and by crackers to compromise it. To portscan a host is to scan for listening ports on a single target host.

1. Nmap
2. Superscan
3. Angry Ip Scanner

1. Nmap

Nmap (“Network Mapper”) is a free and open source utility for network exploration or security auditing. Many systems and network administrators also find it useful for tasks such as network inventory, managing service upgrade schedules, and monitoring host or service uptime. 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 was designed to rapidly scan large networks, but works fine against single hosts. Nmap runs on all major computer operating systems, and both console and graphical versions are available.

www.nmap.org

2. Superscan :

SuperScan is a powerful freeware TCP port scanner, that includes a variety of additional networking tools like ping, traceroute, HTTP HEAD, WHOIS and more. It uses multi-threaded and asynchronous techniques resulting in extremely fast and versatile scanning. You can perform ping scans and port scans using any IP range or specify a text file to extract addresses from. Other features include TCP SYN scanning, UDP scanning, HTML reports, built-in port description database, Windows host enumeration, banner grabbing and more.

www.foundstone.com/us/resources/proddesc/superscan.htm

3. Angry Ip Scanner :

Angry IP Scanner (or simply ipscan) is an open-source and cross-platform network scanner designed to be fast and simple to use. It scans IP addresses and ports as well as has many other features.

It is widely used by network administrators and just curious users around the world, including large and small enterprises, banks, and government agencies.

It runs on Linux, Windows, and Mac OS X, possibly supporting other platforms as well.

www.angryziber.com/w/Home