Free port scanning software for windows

AutoNOC Port Scan will rapidly analyze a PC to identify the available ports on a remote machine (and potentially vulnerable to break in).
AutoNOC Port Scan runs in parallel to instantly evaluate the services available on a remote device or node.

ReconPortScanner is a free and useful port scanner that allows you to scan and display opened TCP ports. ReconPortScanner is a free and useful port scanner that allows you to scan and display opened TCP ports.
ReconPortScanner lets you monitor all your open ports.

Multi-socket scanner capable of scanning local and remote ports quickly, even on slower machines.

Not the best port scanner around but it works well and quite fast. It is useful for security audit of your personal computer.
Faltron Port Scanner scans for TCP listening/open ports on your or remote system. You can scan a range of ports or just a single port. You SHOULD NOT scan others system without their permission! I will not held responsible if you use it for illegal purposes.
The speed will be a bit slower when scanning remote system. You can double click on an open port to view more information on the DShield website.

A port scanner is a must have tool for the network administrator. It allows you to scan your network for active ports. This way you can identify applications such as web servers, ftp servers etc. running on your servers and workstations. Any unused applications should be stopped. Furthermore, you can scan your network for ports that might be used by Trojans.The LANguard port Scanner can be used to: - Scan newly installed systems for active services that are not needed or not configured properly. - Scan for newly added ports that might indicate Trojan activity - Check proxy firewall ports - Test router access lists - Perform basic security checks - Look for reverse telnet ports - Verify available network servicesThe LANguard port scanner is freeware.

HighSpeed Port Scanner is a free tool intended for fast search of open ports. Search can be carried out both in a local network, and on the Internet.
Speed of scanning reaches more than 2500 ports per second!
This program doesn?t use the multi-thread algorithm therefore it is not required the big resources in an operating time.
The HighSpeed Port Scanner has three modes of speed of scanning: low, medium and high. Use of each of these modes depends on speed of connection.

NetworkActiv Port Scanner 4 makes it easy to scan and explore internal LANs and external WANs. Because of the versatility and choosable operating modes available in NetworkActiv Port Scanner, it may be used by experienced network administrators as well as by novices. NetworkActiv Port Scanner provides all the basic features that you'd expect in an advanced network scanner, but also provides many additional features and technologies, some of which being completely unique to this scanner. NetworkActiv Port Scanner provides scanning performance simply not found in other Windows based network scanners, but one will need to actually try it to understand just how fast a network scan can be.