[ale] lightweight testing for remote services

[Chris Fowler]

I Know that for TCP, you can do a simple connect() and if it fails you
have a service down.  But from M$ world we've learned that in some cases
it is possible for the kernel to accept the conneciton but the service
does not respond.

In perl you can use IO::Socket::INET to do a simple connect test.  UDP
is a totallty different story.  Many UDP protocols are a form of
communications that do not use a connect() to start the talk.  To test
DNS services, you may actually have to build a DNS query and send it. 
When you get a response you'll know it is up.

Big Brother can do some of this monitoring for you.  

-- connect test --

#!/usr/bin/perl
$sock = new IO:Socket::INET(PeerAddr => $TARGET,
                            PeerPort => $PORT,
                            Proto    => 'tcp') or
  die "Could not create socket $!\n";

---- end --

That could be your simple lightweight connect test.

I've had problems with nmap detecting my natted ports.  Not sure why.

On Fri, 2003-03-21 at 09:06, Stephen Leonard wrote:
> Keith Hopkins <hne at hopnet.net> writes:
> 
> > Hi folks,
> > 
> >   Anyone know a lightweight way to test if a service (dns,http,ssh,insert-your-favorite-protocol-here) is being serviced on a remote server?
> 
> Mon is a nice (robust) tool for monitoring remote services.  It
> may not be lighter than your nmap script, but it provides a nice
> way to test if services are alive (like pulling an index page to
> test http).  It also has several other features such as automatic
> paging.
> 
> http://www.kernel.org/software/mon
> 
> hth,
> stephen
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