Really, there are two problems - why host is unreachable and why "Bad arg length" error appears.

You could read the discussion of both the problems here. Solution is in Msg5.

For impatient:

Host is unreachable because Net::Ping being used with UDP or TCP checks it via echo service (port 7). This service is down by default on some linux and BSD (one man said me that it is due to security reason). Solution: use ICMP (and run as root) or switch on echo service on remote host.

"Bad arg length" error appears if remote host is unreachable (may be it is the result of the first problem). Simple patch to Net::Ping - while waiting package you should check return value of recv and do nothing if it is false.

Patch for Net::Ping 2.02 - change line 373

to

and you will have remote host unreachable instead of the error.

Could anybody tell me - where and how should I officially submit this patch?

answers available here (CPAN FAQ):
How do I report/fix a bug in Perl and/or its documentation?
How do I report/fix a bug in a module/script?
Have a nice day
All decision is left to your taste

#!/usr/bin/perl
use Net::Ping;
$p = Net::Ping->new('icmp');
print "She's workin\n" if $p->ping("ns.online.no");
$p->close();
[download]

zodiac:/home/perl# ./test1.pl
She's workin
zodiac:/home/perl#
[download]

#!/usr/bin/perl
use Net::Ping;
$p = Net::Ping->new('icmp');
print "She's workin\n" if $p->ping("ns.online.no");
$p->close();
[download]

#!/usr/bin/perl
use Net::Ping;
$p = Net::Ping->new();
print "She's workin\n" if $p->ping("ns.online.no");
$p->close();
[download]

i ran into this problem a while back.

Net::Ping requires UID 0 ( as already noted ) to run ICMP pings.

the other services ( TCP and UDP ) need to be implemented and accessible on the receiving host. the default proto is UDP according to the docs.

1. Read docs carefully.
2. icmp MAY need suid 0 , udp and tcp don't.
3. tcp just connects no data is transfered or echo'ed, so if you just want test if target host is alive use tcp.
4. Your example is little vague on target address. Make sure your target is a host, not a domain. Not all domains, (ie foo.com) have corresponding hosts (ie yahoo.com DOES, kingkong.com DOES NOT).
5. Net::Ping will accept fully qualified host nmaes and IP numbers they do not require packing
6. Suggest using IP numbers first until you have it working. Try good old ping('127.0.0.1')

mitd-Made in the Dark
'My favourite colour appears to be grey.'

Update Great answer brother ab which leads me to a clarification of my point 3. tcp just connects...

Yes tcp does just connect and does not transfer data but connect is through tcp echo service port so, as brother ab points out, if tcp echo service is turned off in inetd.conf we is poop out of luck.

Again, thanks brother ab for clearing some past mysteries for me as well. Your answer got a ++ vote from moi ! :)

mitd-Made in the Dark
'My favourite colour appears to be grey.'

#!/usr/bin/perl

@pinglist=("www.yahoo.com", "www.thisisntreal.com", "wlindsey.bbcg.com
+");

use Net::Ping;
sub test_ping;

foreach $h (@pinglist) {
    if (test_ping($h)) { print "[p (ok) $h]"; } else { print "[p <NO> 
+$h]"; }
    print "\n";
}

sub test_ping { # test_ping($hostname)
    my $hostname=shift;
    my $p=Net::Ping->new(icmp,5);
    return $p->ping($h,5);
    $p->close;
}   # end test_ping
[download]

JP