Re: testing a udp socket with netcat

[Chris Davies <chris-usenet@roaima.co.uk>]

Arif Hossain <freefall1986@gmail.com> wrote:
> i've this udp daemon which is waiting for an incoming udp datagram [...]
> problem is if I issue following command for putting udp datagram :
> $nc -uvvz <host> <port>
> it does not output any thing

UDP is connectionless, so you cannot check whether there is something
listening simply by connecting to the port. This is documented in
the netcat man page:

  CAVEATS
       UDP port scans will always succeed (i.e. report the port as open),
       rendering the -uz combination of flags relatively useless.

Chris