Solid KNOWN good program for TCP and UDP port scanning

I need to know if anyone can recommend to me a VERY solid TCP/UDP port scanning piece of software?
I need to run this on various network items that I have (some PCs, some not PCs) ... I know what port
I am looking for, and if it is NOT open on the 'box', then I know something is not set right.

The problem I've found so far is that MOST port scanners are the SAME for TCP, but they mostly fall short
when scanning for UDP ports?  Why is this?

What is the difference when scanning port .... why are the methods used?
What is the difference between scanning for open TCP ports vs. UDP ports?
Why is it that there a lots of options for scanning TCP ports (most all programs have the same options), but
when it comes to properly scanning for UDP ports ... some scanners list the UDP port open and others do NOT?

Thanks in advance for your time and any reply!
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This is a very useful "book" that sheds light on several of you questions concerning TCP and UDP.  Personally, I alway use Ethereal for network scanning.  It is capable of being filtered so that you know what port or what protocol a particular IP is using.  If you go to you can read more about it. Hope this helps!!

Port scanning - NMAP
This is not a vulnerability analysis tool, just a port scanner.

I'll get into answering some of your other questions later. But the best scanner for TCP/UDP ports for me is nmap (

Which scanners are you seeing that can't scan UDP?

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pugdog_fanAuthor Commented:
I can SCAN UDP ... for the most part ... some scanners list many different UDP options (some that others don't list).  When it comes to scanning TCP, all the programs seem to all have the same options.

I know this PBX box I'm working with should have UDP port 5060 OPEN ... When I scan its IP ... it never shows UDP 5060 open.
I have seen a program that did list it open before, but I can't recall that program name.

Finally, is nmap available in a Windows version?  
Yes, nmap is available for Windows Just scroll down when you're in the download section.
BTW - You have to run nmap from the command line.

You can also try SuperScan
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Networking Protocols

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