Net::Ping(3p) Perl Programmers Reference Guide Net::Ping(3p)
Net::Ping - check a remote host for reachability
use Net::Ping;
$p = Net::Ping->new();
print "$host is alive.\n" if $p->ping($host);
$p->close();
$p = Net::Ping->new("icmp");
$p->bind($my_addr); # Specify source interface of pings
foreach $host (@host_array)
{
print "$host is ";
print "NOT " unless $p->ping($host, 2);
print "reachable.\n";
sleep(1);
}
$p->close();
$p = Net::Ping->new("tcp", 2);
# Try connecting to the www port instead of the echo port
$p->{port_num} = getservbyname("http", "tcp");
while ($stop_time > time())
{
print "$host not reachable ", scalar(localtime()), "\n"
unless $p->ping($host);
sleep(300);
}
undef($p);
# Like tcp protocol, but with many hosts
$p = Net::Ping->new("syn");
$p->{port_num} = getservbyname("http", "tcp");
foreach $host (@host_array) {
$p->ping($host);
}
while (($host,$rtt,$ip) = $p->ack) {
print "HOST: $host [$ip] ACKed in $rtt seconds.\n";
}
# High precision syntax (requires Time::HiRes)
$p = Net::Ping->new();
$p->hires();
($ret, $duration, $ip) = $p->ping($host, 5.5);
printf("$host [ip: $ip] is alive (packet return time: %.2f ms)\n", 1000 * $duration)
if $ret;
$p->close();
# For backward compatibility
print "$host is alive.\n" if pingecho($host);
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This module contains methods to test the reachability of
remote hosts on a network. A ping object is first created
with optional parameters, a variable number of hosts may be
pinged multiple times and then the connection is closed.
You may choose one of six different protocols to use for the
ping. The "tcp" protocol is the default. Note that a live
remote host may still fail to be pingable by one or more of
these protocols. For example, www.microsoft.com is generally
alive but not "icmp" pingable.
With the "tcp" protocol the ping() method attempts to estab-
lish a connection to the remote host's echo port. If the
connection is successfully established, the remote host is
considered reachable. No data is actually echoed. This
protocol does not require any special privileges but has
higher overhead than the "udp" and "icmp" protocols.
Specifying the "udp" protocol causes the ping() method to
send a udp packet to the remote host's echo port. If the
echoed packet is received from the remote host and the
received packet contains the same data as the packet that
was sent, the remote host is considered reachable. This
protocol does not require any special privileges. It should
be borne in mind that, for a udp ping, a host will be
reported as unreachable if it is not running the appropriate
echo service. For Unix-like systems see inetd(8) for more
information.
If the "icmp" protocol is specified, the ping() method sends
an icmp echo message to the remote host, which is what the
UNIX ping program does. If the echoed message is received
from the remote host and the echoed information is correct,
the remote host is considered reachable. Specifying the
"icmp" protocol requires that the program be run as root or
that the program be setuid to root.
If the "external" protocol is specified, the ping() method
attempts to use the "Net::Ping::External" module to ping the
remote host. "Net::Ping::External" interfaces with your
system's default "ping" utility to perform the ping, and
generally produces relatively accurate results. If
"Net::Ping::External" if not installed on your system,
specifying the "external" protocol will result in an error.
If the "syn" protocol is specified, the ping() method will
only send a TCP SYN packet to the remote host then immedi-
ately return. If the syn packet was sent successfully, it
will return a true value, otherwise it will return false.
NOTE: Unlike the other protocols, the return value does NOT
determine if the remote host is alive or not since the full
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TCP three-way handshake may not have completed yet. The
remote host is only considered reachable if it receives a
TCP ACK within the timeout specifed. To begin waiting for
the ACK packets, use the ack() method as explained below.
Use the "syn" protocol instead the "tcp" protocol to deter-
mine reachability of multiple destinations simultaneously by
sending parallel TCP SYN packets. It will not block while
testing each remote host. demo/fping is provided in this
distribution to demonstrate the "syn" protocol as an exam-
ple. This protocol does not require any special privileges.
Functions
Net::Ping->new([$proto [, $def_timeout [, $bytes [, $device [,
$tos ]]]]]);
Create a new ping object. All of the parameters are
optional. $proto specifies the protocol to use when
doing a ping. The current choices are "tcp", "udp",
"icmp", "stream", "syn", or "external". The default is
"tcp".
If a default timeout ($def_timeout) in seconds is pro-
vided, it is used when a timeout is not given to the
ping() method (below). The timeout must be greater than
0 and the default, if not specified, is 5 seconds.
If the number of data bytes ($bytes) is given, that many
data bytes are included in the ping packet sent to the
remote host. The number of data bytes is ignored if the
protocol is "tcp". The minimum (and default) number of
data bytes is 1 if the protocol is "udp" and 0 other-
wise. The maximum number of data bytes that can be
specified is 1024.
If $device is given, this device is used to bind the
source endpoint before sending the ping packet. I
beleive this only works with superuser privileges and
with udp and icmp protocols at this time.
If $tos is given, this ToS is configured into the
soscket.
$p->ping($host [, $timeout]);
Ping the remote host and wait for a response. $host can
be either the hostname or the IP number of the remote
host. The optional timeout must be greater than 0
seconds and defaults to whatever was specified when the
ping object was created. Returns a success flag. If
the hostname cannot be found or there is a problem with
the IP number, the success flag returned will be undef.
Otherwise, the success flag will be 1 if the host is
reachable and 0 if it is not. For most practical
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purposes, undef and 0 and can be treated as the same
case. In array context, the elapsed time as well as the
string form of the ip the host resolved to are also
returned. The elapsed time value will be a float, as
retuned by the Time::HiRes::time() function, if hires()
has been previously called, otherwise it is returned as
an integer.
$p->source_verify( { 0 | 1 } );
Allows source endpoint verification to be enabled or
disabled. This is useful for those remote destinations
with multiples interfaces where the response may not
originate from the same endpoint that the original des-
tination endpoint was sent to. This only affects udp and
icmp protocol pings.
This is enabled by default.
$p->service_check( { 0 | 1 } );
Set whether or not the connect behavior should enforce
remote service availability as well as reachability.
Normally, if the remote server reported ECONNREFUSED, it
must have been reachable because of the status packet
that it reported. With this option enabled, the full
three-way tcp handshake must have been established suc-
cessfully before it will claim it is reachable. NOTE:
It still does nothing more than connect and disconnect.
It does not speak any protocol (i.e., HTTP or FTP) to
ensure the remote server is sane in any way. The remote
server CPU could be grinding to a halt and unresponsive
to any clients connecting, but if the kernel throws the
ACK packet, it is considered alive anyway. To really
determine if the server is responding well would be
application specific and is beyond the scope of
Net::Ping. For udp protocol, enabling this option
demands that the remote server replies with the same udp
data that it was sent as defined by the udp echo ser-
vice.
This affects the "udp", "tcp", and "syn" protocols.
This is disabled by default.
$p->tcp_service_check( { 0 | 1 } );
Depricated method, but does the same as service_check()
method.
$p->hires( { 0 | 1 } );
Causes this module to use Time::HiRes module, allowing
milliseconds to be returned by subsequent calls to
ping().
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This is disabled by default.
$p->bind($local_addr);
Sets the source address from which pings will be sent.
This must be the address of one of the interfaces on the
local host. $local_addr may be specified as a hostname
or as a text IP address such as "192.168.1.1".
If the protocol is set to "tcp", this method may be
called any number of times, and each call to the ping()
method (below) will use the most recent $local_addr. If
the protocol is "icmp" or "udp", then bind() must be
called at most once per object, and (if it is called at
all) must be called before the first call to ping() for
that object.
$p->open($host);
When you are using the "stream" protocol, this call pre-
opens the tcp socket. It's only necessary to do this if
you want to provide a different timeout when creating
the connection, or remove the overhead of establishing
the connection from the first ping. If you don't call
"open()", the connection is automatically opened the
first time "ping()" is called. This call simply does
nothing if you are using any protocol other than stream.
$p->ack( [ $host ] );
When using the "syn" protocol, use this method to deter-
mine the reachability of the remote host. This method
is meant to be called up to as many times as ping() was
called. Each call returns the host (as passed to
ping()) that came back with the TCP ACK. The order in
which the hosts are returned may not necessarily be the
same order in which they were SYN queued using the
ping() method. If the timeout is reached before the TCP
ACK is received, or if the remote host is not listening
on the port attempted, then the TCP connection will not
be established and ack() will return undef. In list
context, the host, the ack time, and the dotted ip
string will be returned instead of just the host. If the
optional $host argument is specified, the return value
will be partaining to that host only. This call simply
does nothing if you are using any protocol other than
syn.
$p->nack( $failed_ack_host );
The reason that host $failed_ack_host did not receive a
valid ACK. Useful to find out why when ack(
$fail_ack_host ) returns a false value.
$p->close();
Close the network connection for this ping object. The
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network connection is also closed by "undef $p". The
network connection is automatically closed if the ping
object goes out of scope (e.g. $p is local to a subrou-
tine and you leave the subroutine).
pingecho($host [, $timeout]);
To provide backward compatibility with the previous ver-
sion of Net::Ping, a pingecho() subroutine is available
with the same functionality as before. pingecho() uses
the tcp protocol. The return values and parameters are
the same as described for the ping() method. This sub-
routine is obsolete and may be removed in a future ver-
sion of Net::Ping.
There will be less network overhead (and some efficiency in
your program) if you specify either the udp or the icmp pro-
tocol. The tcp protocol will generate 2.5 times or more
traffic for each ping than either udp or icmp. If many
hosts are pinged frequently, you may wish to implement a
small wait (e.g. 25ms or more) between each ping to avoid
flooding your network with packets.
The icmp protocol requires that the program be run as root
or that it be setuid to root. The other protocols do not
require special privileges, but not all network devices
implement tcp or udp echo.
Local hosts should normally respond to pings within mil-
liseconds. However, on a very congested network it may take
up to 3 seconds or longer to receive an echo packet from the
remote host. If the timeout is set too low under these con-
ditions, it will appear that the remote host is not reach-
able (which is almost the truth).
Reachability doesn't necessarily mean that the remote host
is actually functioning beyond its ability to echo packets.
tcp is slightly better at indicating the health of a system
than icmp because it uses more of the networking stack to
respond.
Because of a lack of anything better, this module uses its
own routines to pack and unpack ICMP packets. It would be
better for a separate module to be written which understands
all of the different kinds of ICMP packets.
The latest source tree is available via cvs:
cvs -z3 -q -d :pserver:anonymous@cvs.roobik.com.:/usr/local/cvsroot/freeware checkout Net-Ping
cd Net-Ping
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The tarball can be created as follows:
perl Makefile.PL ; make ; make dist
The latest Net::Ping release can be found at CPAN:
$CPAN/modules/by-module/Net/
1) Extract the tarball
gtar -zxvf Net-Ping-xxxx.tar.gz
cd Net-Ping-xxxx
2) Build:
make realclean
perl Makefile.PL
make
make test
3) Install
make install
Or install it RPM Style:
rpm -ta SOURCES/Net-Ping-xxxx.tar.gz
rpm -ih RPMS/noarch/perl-Net-Ping-xxxx.rpm
For a list of known issues, visit:
https://rt.cpan.org/NoAuth/Bugs.html?Dist=Net-Ping
To report a new bug, visit:
https://rt.cpan.org/NoAuth/ReportBug.html?Queue=Net-Ping
Current maintainer:
bbb@cpan.org (Rob Brown)
External protocol:
colinm@cpan.org (Colin McMillen)
Stream protocol:
bronson@trestle.com (Scott Bronson)
Original pingecho():
karrer@bernina.ethz.ch (Andreas Karrer)
pmarquess@bfsec.bt.co.uk (Paul Marquess)
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Original Net::Ping author:
mose@ns.ccsn.edu (Russell Mosemann)
Copyright (c) 2002-2003, Rob Brown. All rights reserved.
Copyright (c) 2001, Colin McMillen. All rights reserved.
This program is free software; you may redistribute it
and/or modify it under the same terms as Perl itself.
$Id: Ping.pm,v 1.7 2003/12/03 03:02:39 millert Exp $
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