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.