> > What are some good methods to test UDP filters port by port?
> What about something like 'strobe' or 'netcat' ?
Well ... you often won't get back too much: there's no such thing
as a RST packet in UDP ... maybe you'll get ICMP port unreachable
but these may be supressed.
Best bet would be to put up a sniffer before and after the filter
element, hit it with the packets and see what's getting through
(or sent back to the source).
BTW, this is useful for TCP, too, especially when sending
non-standard format packets (like etcp and friends).