use LWP::UserAgent;
$ua = new LWP::UserAgent;
$ua->agent("AgentName/0.1 " . $ua->agent);

my $req = new HTTP::Request GET => "http://some.server.net/";
my $res = $ua->request($req);

if ($res->is_success) {
   #server is alive, do something
}
else {
   #something wrong, do something
}
[download]

update:

see this node for an excellent example.

good luck!

my $req = new HTTP::Request HEAD => "http://some.server.net/";
my $res = $ua->request($req);
[download]

This is still assuming that HTTP is indeed the service of interest.

Matt

Like merlyn says, just be sure that if the HEAD fails try again with a GET. Many servers are configured not to respond to HEAD requests.

Did you specify a timeout period for ping? You can use -t to tell ping when you want it to exit. Here's some code that returns true if the remote machine pings at least once in 7 seconds:

sub ping {
  my $ip = shift;
  my $p = `/sbin/ping -c 5 -t 7 $ip | /usr/bin/grep 'packet loss'`;
  unless ( $p =~ /(\d+)% packet loss/ ) {
    die ( "Bad Response:\n$p\n" );
  }
  my $loss = $1;
  print "Loss = $1 ";
  return ( $loss != 100 );
}
[download]

Are you on RedHat? iputils-ss001110 uses -t for time-to-live. I've got -w for timeout. Oh well, no matter.

tnx very much guys! i really appreciated the help. even though my question was not specific. im really sorry about it. my question shouldve been like this:

In general IO::Socket process (regardless of which socket and what typ
+e of socket to use) what should be the recommended process to detect 
+if the remote machines are alive/reachable if you dont want to put a 
+DIE command after the IO::Socket::INET->new() process? (of course, to
+ avoid HANG and probably you would have other codes to execute after 
+the socket connect process...)
[download]

The only thing I thought about at that time was PING. And yes I did forget to check the man pages, sorry for that. heres what i did.:

sub doit
{
$host="$aa.$bb.$cc.$dd";
$port="23";
$fnd="";


$pong=`ping -c 3 $host -v`;    #is there really a "-t" option here?
$fnd=($pong=~m/(...)%/gi);
$xcd=$1;  

 if ($xcd!=100)
 {    

$remote = IO::Socket::INET -> new (
             Proto => "tcp",
             PeerAddr => $host,
             PeerPort => $port,
             Timeout => 1
             );
$| = 1;


if ($remote) 
{
close $remote;
print "Socket ready...";
}
else
{
print "Try again!";
}
}  
 }
[download]

tnx really a lot for helping me. but i do have one inquiry though. "Is there a way to detect remote machines if they are alive/reachable w/o using NET::Ping and the shell command /sbin/ping?" Hopefully something like a socket command. thank you very much to all those who helped me. Lovelots and *mwah*, Cherry.

odd you should say that. I use almost exactly the same code and I have never been troubled with lengthy delays. Are you sure you don't have a problem with DNS name resolution (even though your example shows the use of numeric IP addresses)?

Here is the code I use. It is part of a CGI script, so there is a $q CGI object hanging around, and a few constant values for pretty colors, such as use constant PAINT_OK => '#008000' and so on.

sub test_socket {
    my $s = IO::Socket::INET->new( @_, Timeout=>2, Proto => 'tcp' );
    if( $s ) {
        close $s;
        $q->font( {-color=>PAINT_OK},  'ok' );
    }
    else {
        $q->font( {-color=>PAINT_NOK}, $! )
    }
}

my %tcp_probe = (
    'foo<br>Apache'   => test_socket( PeerHost => '172.17.0.2',     Pe
+erPort => 80,   ),
    'foo<br>Lotus'    => test_socket( PeerHost => '172.17.0.2',     Pe
+erPort => 1352, ),
    'bar<br>Apache'   => test_socket( PeerHost => '172.17.0.3',     Pe
+erPort => 80,   ),
    'bar<br>Lotus'    => test_socket( PeerHost => '172.17.0.3',     Pe
+erPort => 1352, ),
    'example<br>Apache' => test_socket( PeerHost => 'www.example.com',
+ PeerPort => 80,   ),
    'example<br>Domino' => test_socket( PeerHost => 'www.example.com',
+ PeerPort => 8000, ),
    'example<br>Lotus'  => test_socket( PeerHost => 'www.example.com',
+ PeerPort => 1352, ),
    'Web<br>Proxy'       => test_socket( PeerHost => '172.17.0.9',    
+ PeerPort => 8080, ),
    'baz<br>Sybase' => test_socket( PeerHost => '172.17.0.1',     Peer
+Port => 4100, ),
    'baz<br>Samba'  => test_socket( PeerHost => '172.17.0.1',     Peer
+Port => 139,  ),
);

print $q->h3('Mission Critical'), $q->table(
    $q->TR(
        $q->th( {-width=>60, -valign=>'bottom', -bgcolor=>'#fff0e0'},
            [ sort keys %tcp_probe ]
        )
    )
    . $q->TR(
        $q->td( {-width=>60, -align=>'center'},
            [ map { $tcp_probe{$_} } sort keys %tcp_probe ]
        )
    )
);
[download]

The only other thing I could suggest would be to set an alarm of a second or two, an alarm handler and eval the code, in order to forcibly cancel the code. But if it's blocking at a low enough level, alarm won't necessarily work either, I've had that happen in the past.

tnx guys, ive tried what GRINDER recommended and heres what happened to my code:

use IO::Socket;

sub doit
{
$ip1="210.22.106.31";
$host="$ip1";
$port="23";
$fnd="";

$pong=`ping -c 3 $host`;
$fnd=($pong=~m/(..)%/gi);
$xcd=$1;  

 if ($xcd!=00)
 {    

 $SIG{ALRM} = \&timed_out;
 eval { 
 alarm (3); 
 $remote = IO::Socket::INET -> new (
             Proto => "tcp",
             PeerAddr => $host,
             PeerPort => $port,
         Timeout => 2
             ) or die "." ;
 alarm (0); 
 };
 sub timed_out {
 die ".";
 }

 $| = 1;

if ($remote) 
{
close $remote;
print "Socket ready...\n";
}
else
{
print "Try again...\n";
}
}
else
{
print "Pinged timed out!\n";
}
[download]

This doenst seem to work? It also hangs just as before? sigh... got any substitute for EVAL which works for Sockets? Thank you all for helping me. I really dont know what to do next? Lovelots and *mwah* *mwah* *mwah*, Cherry.

"I pinged your machine so I know it's working, but I can't see your website. What else could be wrong?"