


Net::Ping(3p)    Perl Programmers Reference Guide   Net::Ping(3p)


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
           $p->port_number(getservbyname("http", "tcp"));
           while ($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);





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Net::Ping(3p)    Perl Programmers Reference Guide   Net::Ping(3p)


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



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Net::Ping(3p)    Perl Programmers Reference Guide   Net::Ping(3p)


       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 ]]]]]);
           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.

       $p->ping($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



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           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 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 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.



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       $p->bind($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



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           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.





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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)



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Net::Ping(3p)    Perl Programmers Reference Guide   Net::Ping(3p)



         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 1.9 2009/10/12 18:24:41 millert Exp $








































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