Net::Ping(3p) Perl Programmers Reference Guide Net::Ping(3p) #
Net::Ping(3p) Perl Programmers Reference Guide Net::Ping(3p)
NNAAMMEE #
Net::Ping - check a remote host for reachability
SSYYNNOOPPSSIISS #
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("icmpv6");
$ip = "[fd00:dead:beef::4e]";
print "$ip is alive.\n" if $p->ping($ip);
$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);
DDEESSCCRRIIPPTTIIOONN #
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 ppiinngg(()) 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 ppiinngg(()) 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
iinneettdd(8) for more information.
If the "icmp" protocol is specified, the ppiinngg(()) 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 ppiinngg(()) 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. This protocol does not require any special privileges.
FFuunnccttiioonnss 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 ppiinngg(()) 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
65535, but staying below the MTU (1472 bytes for ICMP) is
recommended. Many small devices cannot deal with fragmented ICMP
packets.
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 TTiimmee::::HHiiRReess::::ttiimmee(())
function, if hhiirreess(()) 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 sseerrvviiccee__cchheecckk(()) method.
$p->hires( { 0 | 1 } );
With 1 causes this module to use Time::HiRes module, allowing
milliseconds to be returned by subsequent calls to ppiinngg(()).
$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 _N_Y_I
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 ppiinngg(()) method (below) will use the
most recent $local_addr. If the protocol is "icmp" or "udp", then
bbiinndd(()) must be called at most once per object, and (if it is called
at all) must be called before the first call to ppiinngg(()) for that
object.
The bbiinndd(()) call can be omitted when specifying the "bind" option to
nneeww(()).
$p->message_type([$ping_type]);
When you are using the "icmp" protocol, this call permit to change
the message type to 'echo' or 'timestamp' (only for IPv4, see RFC
792).
Without argument, it returns the currently used icmp protocol message
type. By default, it returns 'echo'.
$p->open($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 nneeww(()).
$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 ppiinngg(()) was called. Each call returns the host
(as passed to ppiinngg(())) 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 ppiinngg(()) 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 aacckk(()) will return undef. In list context, the
host, the ack time, the dotted ip string, and the port number 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])
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->cclloossee(());
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"'
NNOOTTEESS #
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.
IINNSSTTAALLLL #
The latest source tree is available via git:
git clone https://github.com/rurban/Net-Ping.git
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.
BBUUGGSS #
For a list of known issues, visit:
<https://rt.cpan.org/NoAuth/Bugs.html?Dist=Net-Ping> and
<https://github.com/rurban/Net-Ping/issues>
To report a new bug, visit:
<https://github.com/rurban/Net-Ping/issues>
AAUUTTHHOORRSS #
Current maintainers:
perl11 (for cperl, with IPv6 support and more)
p5p (for perl5)
Previous maintainers:
bbb@cpan.org (Rob Brown)
Steve Peters
External protocol:
colinm@cpan.org (Colin McMillen)
Stream protocol:
bronson@trestle.com (Scott Bronson)
Wake-on-lan:
1999-2003 Clinton Wong
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)
CCOOPPYYRRIIGGHHTT #
Copyright (c) 2017-2020, Reini Urban. All rights reserved.
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 v5.36.3 2023-02-15 Net::Ping(3p)