> Getting practical for a minute. What is the optimal way now to see > if a given host truly exists?
You first have to define what you mean by 'exists'. I have a machine here that I call 'stinky'. It's not on the Interent though. Does the 'host' 'stinky' exist? > Assume that I can't control the DNS > server--I need to have this code run in any (*ix) environment. > Assume also that I don't want to run around specialcasing specific IP > addresses or TLDs--this needs to work reliably no matter what the > domain. User gives me a string, and I need to see if the given host > is a real machine. How would you do this before? Does an A record for a hostname mean that a host with that name exists? If so, then all *.com 'hosts' now 'exist'. If not, what did you mean by exist before? > An answer from Verisign would be most appropriate here, since they > have done "extensive research" on the impact of their new service, so > presumably they figured out the answer to this problem and have code > samples available for distribution. However I get the feeling from > their press releases that they've forgotten there is more to the > internet than just the web. Forgive me for defending Verisign, but if you want to know if a given DNS name corresponds with an A record, you can still determine that. If you want to determine something else, you can still do that, depending upon what that something else is. As for 'fsck.de', a good argument can be made that this is not really a legal domain. It's a host. Checking for an SOA is a good way to tell if a domain is valid, depending upon what you mean by 'domain' and 'valid'. I'm reminded of the classic programmers question, "how do you tell if a machine is online?". The answer is "define what you mean by a machine being online and test for that". So you aren't asking a comprehensible question yet. DS