How can I quickly find all the listening or open ports on my computer?

These tools will show you the ports that are open or closed on your computer.

Net Monitor v0.90

Shows listening and connected ports and logs them to a file if you want.

Download the free 0.90 version from HERE (251kb)

Sysinternals TCPView v2.33

This tool will also show the process name that has the port opened and will let you terminate it. The program will also show newly-connected ports in green, while closed ports will be colored in red.

Download from HERE or from THERE (35kb)

LPS - Local Port Scanner 1.2.2

Freeware, will scan for any given local port, has some built-in Trojan detection functionality. Also lets you scan a remote system and will log the output.

Download from HERE or from THERE (562kb)

Smartline Active Ports v1.4

Freeware, easy to use tool for Windows NT/2000/XP that enables you to monitor all open TCP and UDP ports on the local computer. Active Ports maps ports to the owning application so you can watch which process has opened which port. It also displays a local and remote IP address for each connection and allows you to terminate the owning process. Active Ports can help you to detect Trojans and other malicious programs.

Note: This tool seems not to work under Windows Server 2003.

Download from HERE or from THERE (450kb)