RE: verifying an open or closed port on an ip address

you can't determine conclusively whether a port is 'open' from a remote location. what actions does your CPU take when bits arrive on an exposed network interface? If you don't know, then you can't tell whether a port is open. judging a port to be 'open' because it responds to the TCP 3-way handshake and 'closed' otherwise is wrong, even if you only care about TCP and ignore UDP.

-----Original Message-----

From: ian@kingcon.com [mailto:ian@kingcon.com] Sent: Thursday, August 07, 2003 7:45 AM
To: security-basics@securityfocus.com
Subject: verifying an open or closed port on an ip address

Hello,

I am looking for a windows compatible utility or method, preferably command line, where I can verify whether a port on an ip address is reachable or not. I want to be able to do individual ports and not port scans. Say for instance I wish to verify that port 677 is closed to traffic on ip address Ex. 172.16.0.1, I'm looking for a utility that would do something like:

Check 172.16.0.1 port 677

and tell me whether that port was reachable.

So if I have two networks and I use this command from one I can determine whether a port is reachable on another. To determine whether a security measure is failing or not.

There may be a simple way to do this...

Do you need help?

In addition to our free technical library, Pantek provides professional IT services to companies who utilize Open Source software: Learn more about Pantek's Technical Support offerings Place an order for 24/7/365 Technical Support here Learn more about Pantek, who we are, and what we do Chat with a Live Operator Related securityfocus.com Links bugtraq certification focus-bsd focus-ids focus-ih focus-linux focus-ms focus-sun focus-unix-other focus-virus forensics incidents libnet linux-secnews ms-secnews pen-test secpapers secprog sectools secureshell security-basics securityjobs sf-news vuln-dev webappsec Request more information about Pantek

Thanks
Ian
:)

Go to www.missingkids.com

But give an' take's the gospel, an' we'll call the bargain fair, For if you 'ave lost more than us, you crumpled up the square!

Mowgli's real Father...