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
$p->port_number(scalar(getservbyname("http", "tcp")));
while ($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, timeout, bytes, device, tos, ttl, family, host,
port, bind, gateway, retrans, pingstring, source_verify econnrefused
dontfrag IPV6_USE_MIN_MTU IPV6_RECVPATHMTU])
Create a new ping object. All of the parameters are optional and
can be passed as hash ref. All options besides the first 7 must be
passed as hash ref.
"proto" specifies the protocol to use when doing a ping. The
current choices are "tcp", "udp", "icmp", "icmpv6", "stream",
"syn", or "external". The default is "tcp".
If a "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.
Valid "family" values for IPv4:
4, v4, ip4, ipv4, AF_INET (constant)
Valid "family" values for IPv6:
6, v6, ip6, ipv6, AF_INET6 (constant)
The "host" argument implicitly specifies the family if the family
argument is not given.
The "port" argument is only valid for a udp, tcp or stream ping,
and will not do what you think it does. ping returns true when we
get a "Connection refused"! The default is the echo port.
The "bind" argument specifies the local_addr to bind to. By
specifying a bind argument you don't need the bind method.
The "gateway" argument is only valid for IPv6, and requires a IPv6
address.
The "retrans" argument the exponential backoff rate, default 1.2.
It matches the $def_factor global.
The "dontfrag" argument sets the IP_DONTFRAG bit, but note that
IP_DONTFRAG is not yet defined by Socket, and not available on many
systems. Then it is ignored. On linux it also sets IP_MTU_DISCOVER
to IP_PMTUDISC_DO but need we don't chunk oversized packets. You
need to set $data_size manually.
$p->ping($host [, $timeout [, $family]]);
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 } );
With 1 causes this module to use Time::HiRes module, allowing
milliseconds to be returned by subsequent calls to ping().
$p->time
The current time, hires or not.
$p->socket_blocking_mode( $fh, $mode );
Sets or clears the O_NONBLOCK flag on a file handle.
$p->IPV6_USE_MIN_MTU
With argument sets the option. Without returns the option value.
$p->IPV6_RECVPATHMTU
Notify an according IPv6 MTU.
With argument sets the option. Without returns the option value.
$p->IPV6_HOPLIMIT
With argument sets the option. Without returns the option value.
$p->IPV6_REACHCONF NYI
Sets ipv6 reachability IPV6_REACHCONF was removed in RFC3542. ping6
-R supports it. IPV6_REACHCONF requires root/admin permissions.
With argument sets the option. Without returns the option value.
Not yet implemented.
$p->bind($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.
The bind() call can be omitted when specifying the "bind" option to
new().
$p->open($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.
The $host argument can be omitted when specifying the "host" option
to new().
$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.
When new() had a host option, this host will be used. Without host
argument, all hosts are scanned.
$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.
$p->ack_unfork($host)
The variant called by ack() with the syn protocol and $syn_forking
enabled.
$p->ping_icmp([$host, $timeout, $family])
The ping() method used with the icmp protocol.
$p->ping_icmpv6([$host, $timeout, $family]) NYI
The ping() method used with the icmpv6 protocol.
$p->ping_stream([$host, $timeout, $family])
The ping() method used with the stream protocol.
Perform a stream ping. If the tcp connection isn't already open,
it opens it. It then sends some data and waits for a reply. It
leaves the stream open on exit.
$p->ping_syn([$host, $ip, $start_time, $stop_time])
The ping() method used with the syn protocol. Sends a TCP SYN
packet to host specified.
$p->ping_syn_fork([$host, $timeout, $family])
The ping() method used with the forking syn protocol.
$p->ping_tcp([$host, $timeout, $family])
The ping() method used with the tcp protocol.
$p->ping_udp([$host, $timeout, $family])
The ping() method used with the udp protocol.
Perform a udp echo ping. Construct a message of at least the one-
byte sequence number and any additional data bytes. Send the
message out and wait for a message to come back. If we get a
message, make sure all of its parts match. If they do, we are
done. Otherwise go back and wait for the message until we run out
of time. Return the result of our efforts.
$p->ping_external([$host, $timeout, $family])
The ping() method used with the external protocol. Uses
Net::Ping::External to do an external ping.
$p->tcp_connect([$ip, $timeout])
Initiates a TCP connection, for a tcp ping.
$p->tcp_echo([$ip, $timeout, $pingstring])
Performs a TCP echo. It writes the given string to the socket and
then reads it back. It returns 1 on success, 0 on failure.
$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.
$p->mselect
A select() wrapper that compensates for platform peculiarities.
$p->ntop
Platform abstraction over inet_ntop()
$p->checksum($msg)
Do a checksum on the message. Basically sum all of the short words
and fold the high order bits into the low order bits.
$p->icmp_result
Returns a list of addr, type, subcode.
pingecho($host [, $timeout]);
To provide backward compatibility with the previous version of
Net::Ping, a pingecho() subroutine is available with the same
functionality as before. pingecho() uses the tcp protocol. The
return values and parameters are the same as described for the
ping() method. This subroutine is obsolete and may be removed in a
future version of Net::Ping.
wakeonlan($mac, [$host, [$port]])
Emit the popular wake-on-lan magic udp packet to wake up a local
device. See also Net::Wake, but this has the mac address as 1st
arg. $host should be the local gateway. Without it will broadcast.
Default host: '255.255.255.255' Default port: 9
perl -MNet::Ping=wakeonlan -e'wakeonlan "e0:69:95:35:68:d2"'
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 and icmpv6 protocols 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 git:
git clone https://github.com/rurban/net-ping.git Net-Ping
cd Net-Ping
The tarball can be created as follows:
perl Makefile.PL ; make ; make dist
The latest Net::Ping releases are included in cperl and perl5.
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>; (stale)
or call:
perlbug
resp.:
cperlbug
AUTHORS
Current maintainers:
perl11 (for cperl, with IPv6 support and more)
p5p (for perl5)
Previous maintainers:
bbb AT cpan.org (Rob Brown)
Steve Peters
External protocol:
colinm AT cpan.org (Colin McMillen)
Stream protocol:
bronson AT trestle.com (Scott Bronson)
Wake-on-lan:
1999-2003 Clinton Wong
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) 2016, cPanel Inc. All rights reserved.
Copyright (c) 2012, Steve Peters. All rights reserved.
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 v5.26.3 2023-05-18 Net::Ping(3pm)
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