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Basically i have a port scanner. It uses Socket to connect. I need to loop through a list of IP's and for each IP loop through a list of ports. Each port is checked to see if a tcp connection can be made. To add a time out facility for unreachable or fire walled servers I fork each IP check to a new process. this new process includes

$SIG{ "ALRM"} = sub { print "TIME_OUT! at $timeout\n"; exit; };
alarm ($timeout);
[download]

I need to be able to make the main program wait until the child process has either died a natural death or has been killed by it's alarm/exit call. Using wait(); sort of works ... that is the main program seems to run through the loops forking a new process for each IP check (this could be thousands of processes) and then each child seems to get on with it's stuff one at a time. I don't understand why the loops don't just wait for the child to die before starting a new one. I suspect I am using wait() all wrong. A simple way would be to put the IP check part of the script in a separate file and call it with system("./check.pl $ip $port");. But I cant believe it's not possible to do this in one script! A simplified copy of the code so far:-

require 5.002;
require DBI;
use strict;
use Socket;
use POSIX "sys_wait_h";

my ($pid, @port_range, @ip_list, $remote, $port, $timeout, $wait);

#----------- config -----------#

$timeout = 10;
@port_range = qw (8080 6969 80 8081 8080 8000 3128 555 657 889
  1180 1181 1182 1183 1184 1185 11012 25318 25719 6969 886);

@ip_list = qw (196.2.49.19 grunt.mweb.co.za mweb.co.za); #this will be
+ populated dynamically from a DB

#----------- config -----------#


foreach $remote (@ip_list)
{
      foreach (@port_range)
      {
        if ($pid = fork)
          {
            $wait = wait ();
            print
              "Running with port $_ and \$pid $pid \$wait  $wait \$?  
+$? \n";
            $port = $_;

            test ($remote, $port, $pid, $timeout);

            kill 9, $pid or die "KILL FAILED"; #not necessary?
            exit;
          }
      }
}
###########################################################
##                     SUB ROUTINES                      ##
###########################################################

sub test
{
  my $remote =   shift;
  my $port =     shift;
  my $pid =      shift;
  my $timeout =  shift;

  my ($iaddr, $paddr, $proto);

  $SIG{"ALRM"} = sub { print "TIME_OUT! at $timeout\n"; exit; };
  alarm ($timeout);

  $iaddr = inet_aton ($remote) or die "no host: $remote";
  $paddr = sockaddr_in ($port, $iaddr);
  $proto = getprotobyname ('tcp');
  socket (SOCK, PF_INET, SOCK_STREAM, $proto) or die "socket: $!";

  if (connect (SOCK, $paddr))
  {
    print "WE HAVE A CONNECTION!\n"
  } 
  else { die "connect: $!"; }

  close (SOCK) or die "close: $!";

}

exit;
[download]

edited: Fri Apr 25 05:01:24 2003 by jeffa - added readmore tag

In reply to New Child to Wait for First Child to Die by spike_hodge

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