Re: [sitefinder-tech-discuss] Pseudo code please

[Karl Auerbach <karl@cavebear.com>]

On Thu, 16 Oct 2003, Kee Hinckley wrote:

> I'd like to see some pseudo code.
> 
> 1. Given a host name in .com/.net, determine whether the host really exists.

That's an ambiguous question.  For example, some of my computers are 
visible from certain IP addresses only on certain TCP or UDP ports and are 
(hopefully) completely invisible from other IP addresses.

Since the access rules to reach various IP addresses are source IP context
sensitive, it is impossible for a DNS server to know whether a "host"  
(by which I suspect you mean the set of IP addresses found in A records
for a given name) "exists" in the sense that packets can actually be sent
to the "host".

(And, of course there is the reverse situation - a host that is 
unreachable for packets sent *to* it, may be emittiting packets.)

		--karl--



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