Ping not working

ja6025 has asked for the wisdom of the Perl Monks concerning the following question:

Hello all, I am fairly new to perl, having learned it 10 years ago by self training, but then didn't use it until recently. I have some to ping an IP address using a subroutine that works with an array, or with an IP from STDIN, but not from a straight variable. I'm confused! Any help would be appreciated! Thanks! Here are 3 examples of the code, 2 that work, and the one I really need to work that doesn't:

# this does not work
use strict;
use Net::Ping;
use warnings;

my $ip = qw(172.16.1.2);
#
my $works = &pingIp($ip);
#
if ( $works == 1 ) {
  print "does not ping\n";
} else {
  print "pings\n";
}

sub pingIp {
   my $ip1 = shift;
   my $p = Net::Ping->new();
   if ($p->ping($ip1)) {
     print "return is 0\n";
     return 0;
   } else {
     print "return is 1\n";
     return 1;
   }
   $p->close();
}
[download]

If I prompt for an IP rather than set the IP outright, the above works


print "Enter an IP:  ";
chomp (my $ip=<STDIN>);
[download]

Or, if I create an array of IPs and ping each one using the pingIp subroutine, it works

my @IParray = qw(172.16.1.2 172.16.1.3);
foreach my $ip (@IParray) {
  my $works = &pingIp($ip);
  if ( $works == 1 ) {
    print "$ip does not ping\n";
  } else {
    print "$ip pings\n";
  }
}
[download]

Thanks for any help!

Comment on Ping not working Select or Download Code

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Re: Ping not working by VinsWorldcom (Prior) on Mar 11, 2015 at 14:52 UTC
Note that by default Net::Ping uses TCP as the default protocol (TCP echo port 7) which some systems may not respond to even if they are up. To use ICMP, you'll need to set the following AND be root / have admin privilege: `my $p = Net::Ping->new('icmp');` [download]	[reply] [d/l]
Re: Ping not working by toolic (Bishop) on Mar 11, 2015 at 13:32 UTC
FWIW, I tried your 3 methods, and all 3 give me the same result on the 172.16.1.2 ip: "does not ping". Other observation: $p->close(); is never executed because you always return from the sub before you reach that line. From the Net::Ping docs, you don't even need to close when your code is inside a sub.	[reply]
Re^2: Ping not working by ja6025 (Initiate) on Mar 11, 2015 at 14:24 UTC
If you actually try an ip that does ping on your network, it still comes back with "does not ping." I will remove the close and also try the qq. Thanks!	[reply]
Re^3: Ping not working by toolic (Bishop) on Mar 11, 2015 at 14:31 UTC
My point was that I cannot reproduce your inconsistent results. Your 3 methods return "does not ping" on an ip that I can't access, and they all return "pings" on an ip that I can access. By the way, qw vs. qq will make no difference in this case; I'm not sure why the other monk recommended that change.	[reply]
Re: Ping not working by karlgoethebier (Abbot) on Mar 11, 2015 at 12:54 UTC
Try `my $ip = qq(172.16.1.2);` Update: If i run the code you posted with `my $ip = qq(66.39.54.27);` i get: `monks>ping.pl return is 0 pings` [download] Regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply] [d/l] [select]
Re^2: Ping not working by Anonymous Monk on Mar 11, 2015 at 17:53 UTC
If i run the code you posted with `my $ip = qq(66.39.54.27);` Because there's only one item in the `qw//` list, that does not make a difference in this case; the list will return its last item. `use Data::Dumper; my $ip1 = qw(172.16.1.2); my $ip2 = qq(172.16.1.2); my $ip3 = qw(172.16.1.2 172.16.1.3); my $ip4 = qq(172.16.1.2 172.16.1.3); print Dumper($ip1, $ip2, $ip3, $ip4); __END__ $VAR1 = '172.16.1.2'; $VAR2 = '172.16.1.2'; Useless use of a constant ("172.16.1.2") in void context at - line 4. $VAR3 = '172.16.1.3'; $VAR4 = '172.16.1.2 172.16.1.3';` [download] (toolic already pointed this out a little while ago.)	[reply] [d/l] [select]
Re^3: Ping not working by karlgoethebier (Abbot) on Mar 11, 2015 at 18:24 UTC
"...toolic already pointed this out a little while ago." No. He wrote that he isn't sure. But perhaps i posted to fast, may be :-( But i'll take a look at what i did... Update: I tried the `qq` as well as the `qw` version on my Mac and it seems that both ping. I remember that i tried the same stuff on XP at noon but the `qw` version didn't work. But may be i miss something. Unfortunately i can't reproduce this on XP tonight. But i'll be back. And please note, when i concede a possible fault i did (because of answering to fast for some reason or what ever) i consider even one down vote as extremely impolite. Regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply] [d/l] [select]
Re^4: Ping not working by Anonymous Monk on Mar 11, 2015 at 18:46 UTC
Re: Ping not working by Anonymous Monk on Mar 11, 2015 at 15:04 UTC
I haven't used ping in a while, and I can't say whether this is the source of your problem, but I remember reading that trying to send a ping from your program/user (as with Net::Ping) is not always reliable because it might actually require root privileges. Net::Ping::External is a workaround that calls an external ping program. `use Net::Ping::External qw(ping); my $alive = ping(host => "www.perlmonks.org"); print "alive: $alive\n";` [download] Might be more reliable on those OSes supported by Net::Ping::External.	[reply] [d/l]