[CALUG] More UDP foolishness
Eric K. Dickinson
Eric.Dickinson at nih.gov
Fri Apr 14 06:20:59 CDT 2006
Eric K. Dickinson
8778548389 at page.metrocall.com
CNE, GNU/Linux Geek Windows 2000 MCSE, CISSP
Jason C. Miller wrote:
> Heck....why not! Here's my random question for the week... :)
> So, anyway, a lot of troubleshooting and investigation is required with
> the stuff that I work on. For as long as I can remember, I've used
> 'telnet' as the simplest way to determine whether or not a TCP port is
> bound to by an application on a machine. It's simple, quick, easy, and
> comes stock on just about every OS imaginable. It's a good way to
> verify that the 3-way-handshake works on a given port.
> Can't say it's been quite that simple for the UDP side of the house.
> Since UDP is connectionless, the mechanisms for determining if a port is
> bound to is a tad different. Instead of conveniently getting a
> (RST,ACK) TCP reply, UDP relies on the receipt of ICMP 'Destination
> Unreachable' messages to tell it that the port is not open. Typically,
> I've relied on applications like nmap. However, I don't really feel
> like installing it wherever I go. I've also written simple progs to do
> it, but it's very inconvenient.
> So, the question is....can anybody recommend a COMMON program that you
> would find on most operating systems that could be pointed at an
> arbitrary UDP port and would tell you the status of that port? Seems
> like it'd be simple, but I can't seem to think of any at the moment.
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