Testing on my system, I'm not sure the Timeout is working properly for connects.

Try this version with explicit timeouts for attempts over $timeout seconds.

Also, notice the extreme difference in 'user' and 'sys' times :) 

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1135109
# http://perlmonks.org/?node_id=11103970

use strict;
use warnings;
use IO::Socket;
use IO::Select;
use Time::HiRes qw( time );

my @ips = map "192.168.1.$_", 1..20; # your IPs here
my $port = 22; # your port here
my $max = 1000; # somewhat smaller than max "open files"
my $timeout = 1;

my %handles;
my $sel = IO::Select->new;

while( @ips or $sel->count )
  {
  if( @ips and $sel->count < $max )
    {
    my $ip = shift @ips;
    my $fh = IO::Socket::INET->new(PeerHost => $ip, PeerPort => $port,
      Proto => 'tcp', Blocking => 0);
    $handles{$fh} = ["$ip:$port", $fh, time]; 
    $sel->add($fh);
    }
  elsif( @ips ? $sel->count >= $max : $sel->count )
    {
    my @connects;
    for my $fh ( @connects = $sel->can_write($timeout) )
      {
      print $fh->connected ? '   ' : 'not', " alive  $handles{$fh}[0]\
+n";
      $sel->remove($fh);
      delete $handles{$fh};
      }
    if( not @connects )
      {
      my $time = time - $timeout;
      for my $key ( keys %handles )
        {
        if( $handles{$key}[2] < $time )
          {
          print "not alive  $handles{$key}[0]\n";
          $sel->remove( $handles{$key}[1] );
          delete $handles{$key};
          }
        }
      }
    }
  }

[download]

There are several different ways to do the timeouts, I'm curious how this one works out. Others may be slightly faster on wall clock, but use much more CPU.

In reply to Re^3: A question of fork efficiency by tybalt89
in thread A question of fork efficiency by synless

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