Interesting thought. I don't think it would be wise to send a unique identifier in a cookie or query parameter, because it may be going to an arbitrary site, which might not like receiving an unexpected cookie or query parameter. But it could be sent in a custom HTTP header, since according to the HTTP 1.1 specification, unrecognized headers SHOULD be ignored. However, there would still be the issue of generating a unique identifier -- rand would probably be good enough for that -- and sharing it across all of the mod_perl2 threads that handle HTTP requests for my server, which sounds like it would require some kind of locking or mutex. This approach may be worth considering if I cannot find anything easier.

But it seems to me that there must be some reliable way to do this at the OS level, since the OS obviously needs to know all of the IP addresses and ports on which it is listening.

In reply to Re^2: How can I determine whether a URI, hostname or IP address is to the local host machine? by dbooth
in thread How can I determine whether a URI, hostname or IP address is to the local host machine? by dbooth

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