👤
Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:
Select Section of Man Page:
Select Man Page Repository:

RedHat 9 (Linux i386) - man page for net::ping (redhat section 3pm)

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

NAME
       Net::Ping - check a remote host for reachability

       $Id: Ping.pm,v 1.46 2002/12/02 19:17:09 rob Exp $

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
	   $p->{port_num} = getservbyname("http", "tcp");
	   while ($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_num} = 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 con-
       sidered reachable.  No data is actually echoed.	This protocol does not require any spe-
       cial privileges but has higher overhead than the other two 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 rel-
       atively accurate results. If "Net::Ping::External" if not installed on your system, speci-
       fying 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 reach-
       able if it receives a TCP ACK within the timeout specifed.  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 send-
       ing 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 exam-
       ple.  This protocol does not require any special privileges.

       Functions

       Net::Ping->new([$proto [, $def_timeout [, $bytes [, $device ]]]]);
	   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 proto-
	   col 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 beleive this only works with superuser privileges and with udp and
	   icmp protocols at this time.

       $p->ping($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 suc-
	   cess 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 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 origi-
	   nate 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->tcp_service_check( { 0 | 1 } );
	   Set whether or not the tcp 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 success-
	   fully 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 respond-
	   ing well would be application specific and is beyond the scope of Net::Ping.

	   This only affects "tcp" and "syn" protocols.

	   This is disabled by default.

       $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 partaining 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 subrou-
	   tine).

       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.

WARNING
       pingecho() or a ping object with the tcp protocol use alarm() to implement the timeout.
       So, don't use alarm() in your program while you are using pingecho() or a ping object with
       the tcp protocol.  The udp and icmp protocols do not use alarm() to implement the timeout.

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 imple-
       ment tcp or udp echo.

       Local hosts should normally respond to pings within milliseconds.  However, on a very con-
       gested 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

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, 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 v5.8.0				    2002-06-01				   Net::Ping(3pm)


All times are GMT -4. The time now is 12:13 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
×
UNIX.COM Login
Username:
Password:  
Show Password