Free tcp port scan 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.

How wide open is your door?
Scan your computer for open/listening ports used by hackers.

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.

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.

Flash Port Scanner is a fast and simple multithread port scanning tool. The program has a simple interface and its very easy to use.

NetworkActiv Port Scanner is a network exploration and administration tool that will allow you 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 youd 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.
Main features:
- TCP connect() port scanner (standard TCP port scanner).
- TCP SYN port scanner (auxiliary TCP port scanner).
- UDP port scanner with automatic speed control.
- UDP subnet port scanner.
- Ping scanning of subnets (UDP or ICMP).
- TCP subnet port scanner, for finding Web servers and other servers.
- High performance trace-route.
- Remote OS detection: Ability to make an educated guess about the OS (Operating System) of a remote host, this is done by TCP/IP stack fingerprinting.
- Wizard Mode: Walks you through step-by-step to perform network scanning, trace-route, and more.
- Whois Client: Ability to perform whois queries, user may either specify a whois server, or have the program attempt to determine a whois server automatically (works with most domains).
- DNS Dig system: Performs DNS dig queries, user may choose between TCP and UDP, specify a DNS server or have the program attempt to determine the authoritative server automatically (works with most domains).
- Simple Port Scanner Mode.
- Graphical user interface, with skin support.
- Ability to notify user if remote computer being scanned is stealth.
- User configurable maximum speed (ranging from 2 PPS to non-limited).
- Attempts to determine host responses for TCP connect() port scanner and subnet port scanner.
- Common port use list, may help user determine the use of an open port.
- Random order, reverse order, and "Only Scan Known Ports" port scanner capable.
- Ability to save the results of the port scanner, subnet port scanner, and other lists to text files.
- Integration between subnet port scanner, port scanner, Windows(c) clipboard, and other programs - customizable.