Windows

NETSTAT -a

That will give you all connections and listening ports.

Now, for services, NET START will list all services that are running, but NET STOP will NOT list all services that are NOT running! Don't ask why.
So, the better solution for services is to get SERVICE.VBS from the Resource Kit. If you run it with the /L switch, it will list all installed services running and not running. There are other switches with this VBS script that can tell you other service information.

hope this helps

There is a free utility you can download from download.com called Lan Guard Network Scanner. You can use it to scan your system for open ports. It will also give you suggestions on how to close that port or if it is prone to being attacked.

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