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
$p->{port_num} = getservbyname("http", "tcp");
while ($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 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 deter-mine determine
mine 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 simulta-neously simultaneously
neously 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. $proto specifies the protocol to
use when doing a ping. The current choices are "tcp", "udp", "icmp", "stream", "syn", or "exter-nal". "external".
nal". The default is "tcp".
If a default timeout ($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 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. Oth-erwise, Otherwise,
erwise, the success flag will be 1 if the host is reachable and 0 if it is not. For most practi-cal practical
cal 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 end-point endpoint
point that the original destination endpoint was sent to. This only affects udp and icmp proto-col protocol
col 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 } );
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 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 neces-sary necessary
sary 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
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 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 net-work network
work 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 pack-ets. packets.
ets. 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 v5.8.8 2001-09-21 Net::Ping(3pm)
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