Provided by: perl-doc_5.18.2-2ubuntu1.7_all 
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
$p->port_number(scalar(getservbyname("http", "tcp")));
while ($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_number(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 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 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 specified. 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 demonstrate the "syn" protocol as an
example. This protocol does not require any special privileges.
Functions
Net::Ping->new([$proto [, $def_timeout [, $bytes [, $device [, $tos [, $ttl ]]]]]]);
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 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 endpoint before sending
the ping packet. I believe 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 socket.
For icmp, $ttl can be specified to set the TTL of the outgoing packet.
$p->ping($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 returned 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 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 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 successfully
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 service.
This affects the "udp", "tcp", and "syn" protocols.
This is disabled by default.
$p->tcp_service_check( { 0 | 1 } );
Deprecated 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 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 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 argument is specified, the
return value will be pertaining 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).
$p->port_number([$port_number])
When called with a port number, the port number used to ping is set to $port_number
rather than using the echo port. It also has the effect of calling
"$p->service_check(1)" causing a ping to return a successful response only if that
specific port is accessible. This function returns the value of the port that
"ping()" will connect to.
pingecho($host [, $timeout]);
To provide backward compatibility with the previous version 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 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 program) if you specify
either the udp or the icmp protocol. 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 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.