Net::Ping(3pm) Perl Programmers Reference Guide Net::Ping(3pm)
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
$p->port_number(getservbyname("http", "tcp"));
while ($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
]]]]]);
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.
$p->ping($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 AT cvs.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 AT cpan.org (Rob Brown)
External protocol:
colinm AT cpan.org (Colin McMillen)
Stream protocol:
bronson AT trestle.com (Scott Bronson)
Original pingecho():
karrer AT bernina.ch (Andreas Karrer)
pmarquess AT bfsec.uk (Paul Marquess)
Original Net::Ping author:
mose AT ns.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.
perl v5.16.3 2013-03-04 Net::Ping(3pm)
Linux-Distributionen
Huschi als Linux-Admin