| Net::Ping - check a remote host for reachability |
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
$p->port_number(getservbyname("http", "tcp"));
while ($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);
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.
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.
hires()
has been previously called, otherwise it is returned as an integer.
This is enabled by default.
This affects the ``udp'', ``tcp'', and ``syn'' protocols.
This is disabled by default.
service_check() method.
This is disabled by default.
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.
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.
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 $host argument is specified, the return
value will be pertaining to that host only.
This call simply does nothing if you are using any protocol
other than syn.
port_number([$port_number])$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() 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.
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.
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
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)
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 1.86 2003/06/27 21:31:07 rob Exp $
| Net::Ping - check a remote host for reachability |