Re: [hobbit] UDP Port Testing

[henrik (at) hswn.dk (Henrik Stoerner)]

On Thu, Nov 24, 2005 at 12:09:02AM -0500, Jeff Stuart wrote:
> Does anyone know of a plugin (or a way) to test a UDP port?  Yes, I know
> that may sound strange (IE UDP IS stateless) but I need to be able to
> basically test if a port responds or not. 

Since there's no handshake in UDP, there is no general way of testing
a random UDP port like you can with TCP. What you *can* do is send a
packet to the UDP port, and see if you get an ICMP error message back - 
if you do, then you can safely assume that there is no service running
on that port.

The problem is that in many cases you just won't get a reply, in which
case you cannot tell for sure if there is a service running or not.

You can run the nmap port scanner in UDP mode and see what is says, but
the only really sure way of testing a UDP port is to talk to the service
that is supposed to run there, and see if any sensible response comes
back to you.


Regards,
Henrik