Re: OT ping sample code
Re: OT ping sample code
- Subject: Re: OT ping sample code
- From: Igor garnov <email@hidden>
- Date: Mon, 12 Jan 2004 21:57:18 +0300
On Monday, Jan 12, 2004, at 21:29 Europe/Moscow, Jason Linhart wrote:
The thing is, ping is the only way to know if a host is online. But
maybe you know something else?
Ping is not an especially reliable way to tell if a host is online.
Many
sites block pings at their firewall, to help prevent some kinds of
denial
of service attacks and the ping of death attack. Most hosts respond to
pings, but hardly all.
Yes, and my own router D-Link has an option of turning off responding
to pings - once I have really turned it off I appear to be offline to
the folks outside when they ping me.
There is no general way to tell if a host is online without knowing
some
additional information about the host. If you want to know if a web
server is up you would try an HTTP request, if you want to know if an
FTP
server is up you would try an FTP request. Without that kind of
additional information, there isn't any universal solution.
There must be a set of ports used by Windows, Mac and Unix/Linux I
suppose... I mean some 'intersection' of sets of ports the machines on
these OSs would normally listen on.
Regards,
Igor
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