Find out if a host is alive

[Anand Pillai]

Thank You Alex. What I want is actually answered by you.
I would like to find if the server is answering HTTP requests
at port 80.

I checked out pyheartbeat, but I think it is useful only for 
computers in the local area network and not the internet.

-Anand

Alex Martelli <aleax at aleax.it> wrote in message news:<ccCfb.224602$R32.7219630 at news2.tin.it>...
> Anand Pillai wrote:
> 
> > I would like to add a feature to one of my network programs.
> > The requirement is to find out if a server is alive by sending
> > it requests. I know of the standard ICMP ping, and searched
> > for python modules able to 'PING'. The only hit I got was Jeremy
> > Hiltons ping package, written for Python 1.4, and it does not
> > work with the latest Python versions (2.0 upwards).
> 
> http://pynms.sourceforge.net/ does appear to support ICMP, among
> many other things, and to support Python 2.2 (I'd be quite amazed
> if it worked with 2.2 and not with 2.3).
> 
> > Are there other ways of finding out (in a few lines of code)
> > whether a server is alive, apart from the ICMP protocol?
> 
> If you know what services the server is supposed to be running,
> sure.  If you have no idea whatsoever, no way.  It's quite
> imaginable, for example, that a server does not serve ICMP
> (doesn't WANT to be pinged nor tracerouted etc) but only,
> strictly HTTP on port 80/TCP _period_.  If you know that, then
> 'pinging' the server is useless as a way to determine whether
> the server 'is alive'; rather, you would try to bind a socket
> to its TCP port 80, and, depending on your definition of "being
> alive", might claim that just managing to bind that socket is
> enough (or, you might try some short HTTP transaction on the
> socket).
> 
> I've noticed an analogy between people wanting their programs
> to check if "a server is alive" and ones wanting their programs
> to check if "a file exists": the question they pose is rarely
> the one they really need to get answered; for example, the
> mere existence of a file is often of no real interest if the
> program does not have permission to _read_ the file -- and
> the mere "aliveness" of a host is often of no real interest
> if the program does not have permission to _talk_ to the host
> along at least one protocol that's of actual _use_...
> 
> 
> Alex