Net::Ping
Net::Ping(3) Perl Programmers Reference Guide Net::Ping(3)
NAME
Net::Ping - check a remote host for reachability
SYNOPSIS
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);
DESCRIPTION
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 establish a con-
nection to the remote host's echo port. If the connection is success-
fully 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 reach-
able. 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 immediately 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
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 determine 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 demon-
strate the "syn" protocol as an example. 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.
$proto specifies the protocol to use when doing a ping. The cur-
rent choices are "tcp", "udp", "icmp", "stream", "syn", or "exter-
nal". The default is "tcp".
If a default timeout ($def_timeout) in seconds is provided, 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 otherwise. The maximum number of data bytes that can be
specified is 1024.
If $device is given, this device is used to bind the source end-
point 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 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 inter-
faces where the response may not originate from the same endpoint
that the original destination 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 ser-
vice 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().
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 num-
ber 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 determine 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 argu-
ment 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 network
connection is also closed by "undef $p". The network connection is
automatically closed if the ping object goes out of scope (e.g. $p
is local to a subroutine and you leave the subroutine).
pingecho($host [, $timeout]);
To provide backward compatibility with the previous version of
Net::Ping, a pingecho() subroutine is available with the same func-
tionality as before. pingecho() uses the tcp protocol. The return
values and parameters are the same as described for the ping()
method. This subroutine is obsolete and may be removed in a future
version of Net::Ping.
NOTES
There will be less network overhead (and some efficiency in your pro-
gram) if you specify either the udp or the icmp protocol. The tcp pro-
tocol 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 privi-
leges, but not all network devices implement tcp or udp echo.
Local hosts should normally respond to pings within milliseconds.
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 conditions, it will appear that the remote
host is not reachable (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.
INSTALL
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
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
BUGS
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
AUTHORS
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)
Original Net::Ping author:
mose@ns.ccsn.edu (Russell Mosemann)
COPYRIGHT
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 1.86 2003/06/27 21:31:07 rob Exp $
perl v5.8.6 2001-09-21 Net::Ping(3)
