Detecting computers on network

[Cameron Laird]

In article <1122052633.489908.94230 at g49g2000cwa.googlegroups.com>,
gene tani <gene.tani at gmail.com> wrote:
>Hi Sandeep,
>
>i didn't see where you said if these hosts you want to ping are on your
>internal network, or beyond your gateway.  Probably the only truly
>reliable way to maintain an active hosts list is to install a
>ping-sending client on them, like
>
>http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52302
>
>And think about possible legal ramifications of port scanning hosts or
>possibly getting your IP blacklisted by a host's firewall, before you
>do it.
>

Let me shift that excellent summary very slightly:  it might
help to clarify what "active host" means.  In some situations,
managers just want to know, "which of our Web servers respond
to requests for their top-level page?"  If you're dealing with
*that* (or which mail servers are serving mail, or ...), then
it's entirely appropriate simply to perform the operation (to
request a page through HTTP, for example) in question.