[p5sagit/p5-mst-13.2.git] / lib / Net / Ping / README

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

    $Id: Ping.pm,v 1.17 2002/02/18 01:25:11 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);

        # 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 four different protocols to use for the ping. The
    "udp" 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 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 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
    the inetd(8) manpage 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.

  Functions

    Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);
        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" or "icmp". The default is "udp".

        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.

    $p->bind($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.

    $p->ping($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. If the hostname cannot
        be found or there is a problem with the IP number, undef is
        returned. Otherwise, 1 is returned if the host is reachable and 0 if
        it is not. For all practical purposes, undef and 0 and can be
        treated as the same case.

    $p->open($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.

    $p->open($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->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).

    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 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.

AUTHORS
      Current maintainers:
        colinm@cpan.org (Colin McMillen)
        bbb@cpan.org (Rob Brown)

      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) 2001, Colin McMillen. All rights reserved.

    Copyright (c) 2001, Rob Brown. All rights reserved.

    This program is free software; you may redistribute it and/or modify it
    under the same terms as Perl itself.
Commit	Line	Data
505f3f16	1	NAME
	2	Net::Ping - check a remote host for reachability
	3
8e0fc1cd	4	$Id: Ping.pm,v 1.17 2002/02/18 01:25:11 rob Exp $
505f3f16	5
	6	SYNOPSIS
	7	use Net::Ping;
	8
	9	$p = Net::Ping->new();
	10	print "$host is alive.\n" if $p->ping($host);
	11	$p->close();
	12
	13	$p = Net::Ping->new("icmp");
ddbbf559	14	$p->bind($my_addr); # Specify source interface of pings
505f3f16	15	foreach $host (@host_array)
	16	{
	17	print "$host is ";
	18	print "NOT " unless $p->ping($host, 2);
	19	print "reachable.\n";
	20	sleep(1);
	21	}
	22	$p->close();
	23
	24	$p = Net::Ping->new("tcp", 2);
	25	# Try connecting to the www port instead of the echo port
	26	$p->{port_num} = getservbyname("http", "tcp");
	27	while ($stop_time > time())
	28	{
	29	print "$host not reachable ", scalar(localtime()), "\n"
	30	unless $p->ping($host);
	31	sleep(300);
	32	}
	33	undef($p);
	34
	35	# For backward compatibility
	36	print "$host is alive.\n" if pingecho($host);
	37
	38	DESCRIPTION
	39	This module contains methods to test the reachability of remote hosts on
	40	a network. A ping object is first created with optional parameters, a
	41	variable number of hosts may be pinged multiple times and then the
	42	connection is closed.
	43
	44	You may choose one of four different protocols to use for the ping. The
	45	"udp" protocol is the default. Note that a live remote host may still
	46	fail to be pingable by one or more of these protocols. For example,
	47	www.microsoft.com is generally alive but not pingable.
	48
	49	With the "tcp" protocol the ping() method attempts to establish a
	50	connection to the remote host's echo port. If the connection is
	51	successfully established, the remote host is considered reachable. No
	52	data is actually echoed. This protocol does not require any special
	53	privileges but has higher overhead than the other two protocols.
	54
	55	Specifying the "udp" protocol causes the ping() method to send a udp
	56	packet to the remote host's echo port. If the echoed packet is received
	57	from the remote host and the received packet contains the same data as
	58	the packet that was sent, the remote host is considered reachable. This
	59	protocol does not require any special privileges. It should be borne in
	60	mind that, for a udp ping, a host will be reported as unreachable if it
	61	is not running the appropriate echo service. For Unix-like systems see
	62	the inetd(8) manpage for more information.
	63
	64	If the "icmp" protocol is specified, the ping() method sends an icmp
	65	echo message to the remote host, which is what the UNIX ping program
	66	does. If the echoed message is received from the remote host and the
	67	echoed information is correct, the remote host is considered reachable.
	68	Specifying the "icmp" protocol requires that the program be run as root
	69	or that the program be setuid to root.
	70
	71	If the "external" protocol is specified, the ping() method attempts to
	72	use the `Net::Ping::External' module to ping the remote host.
	73	`Net::Ping::External' interfaces with your system's default `ping'
	74	utility to perform the ping, and generally produces relatively accurate
	75	results. If `Net::Ping::External' if not installed on your system,
	76	specifying the "external" protocol will result in an error.
	77
	78	Functions
79
80	Net::Ping->new([$proto [, $def_timeout [, $bytes]]]);
81	Create a new ping object. All of the parameters are optional. $proto
82	specifies the protocol to use when doing a ping. The current choices
83	are "tcp", "udp" or "icmp". The default is "udp".
84
85	If a default timeout ($def_timeout) in seconds is provided, it is
86	used when a timeout is not given to the ping() method (below). The
87	timeout must be greater than 0 and the default, if not specified, is
88	5 seconds.
89
90	If the number of data bytes ($bytes) is given, that many data bytes
91	are included in the ping packet sent to the remote host. The number
92	of data bytes is ignored if the protocol is "tcp". The minimum (and
93	default) number of data bytes is 1 if the protocol is "udp" and 0
94	otherwise. The maximum number of data bytes that can be specified is
95	1024.
96
ddbbf559	97	$p->bind($local_addr);
	98	Sets the source address from which pings will be sent. This must be
	99	the address of one of the interfaces on the local host. $local_addr
	100	may be specified as a hostname or as a text IP address such as
	101	"192.168.1.1".
	102
	103	If the protocol is set to "tcp", this method may be called any
	104	number of times, and each call to the ping() method (below) will use
	105	the most recent $local_addr. If the protocol is "icmp" or "udp",
	106	then bind() must be called at most once per object, and (if it is
	107	called at all) must be called before the first call to ping() for
	108	that object.
	109
505f3f16	110	$p->ping($host [, $timeout]);
	111	Ping the remote host and wait for a response. $host can be either
	112	the hostname or the IP number of the remote host. The optional
	113	timeout must be greater than 0 seconds and defaults to whatever was
	114	specified when the ping object was created. If the hostname cannot
	115	be found or there is a problem with the IP number, undef is
	116	returned. Otherwise, 1 is returned if the host is reachable and 0 if
	117	it is not. For all practical purposes, undef and 0 and can be
	118	treated as the same case.
	119
	120	$p->open($host);
	121	When you are using the stream protocol, this call pre-opens the tcp
	122	socket. It's only necessary to do this if you want to provide a
	123	different timeout when creating the connection, or remove the
	124	overhead of establishing the connection from the first ping. If you
	125	don't call `open()', the connection is automatically opened the
	126	first time `ping()' is called. This call simply does nothing if you
	127	are using any protocol other than stream.
	128
	129	$p->open($host);
	130	When you are using the stream protocol, this call pre-opens the tcp
	131	socket. It's only necessary to do this if you want to provide a
	132	different timeout when creating the connection, or remove the
	133	overhead of establishing the connection from the first ping. If you
	134	don't call `open()', the connection is automatically opened the
	135	first time `ping()' is called. This call simply does nothing if you
	136	are using any protocol other than stream.
	137
	138	$p->close();
	139	Close the network connection for this ping object. The network
	140	connection is also closed by "undef $p". The network connection is
	141	automatically closed if the ping object goes out of scope (e.g. $p
	142	is local to a subroutine and you leave the subroutine).
	143
	144	pingecho($host [, $timeout]);
	145	To provide backward compatibility with the previous version of
	146	Net::Ping, a pingecho() subroutine is available with the same
	147	functionality as before. pingecho() uses the tcp protocol. The
	148	return values and parameters are the same as described for the
	149	ping() method. This subroutine is obsolete and may be removed in a
	150	future version of Net::Ping.
	151
	152	WARNING
	153	pingecho() or a ping object with the tcp protocol use alarm() to
	154	implement the timeout. So, don't use alarm() in your program while you
	155	are using pingecho() or a ping object with the tcp protocol. The udp and
	156	icmp protocols do not use alarm() to implement the timeout.
	157
	158	NOTES
	159	There will be less network overhead (and some efficiency in your
	160	program) if you specify either the udp or the icmp protocol. The tcp
	161	protocol will generate 2.5 times or more traffic for each ping than
	162	either udp or icmp. If many hosts are pinged frequently, you may wish to
	163	implement a small wait (e.g. 25ms or more) between each ping to avoid
	164	flooding your network with packets.
	165
	166	The icmp protocol requires that the program be run as root or that it be
	167	setuid to root. The other protocols do not require special privileges,
	168	but not all network devices implement tcp or udp echo.
	169
	170	Local hosts should normally respond to pings within milliseconds.
	171	However, on a very congested network it may take up to 3 seconds or
	172	longer to receive an echo packet from the remote host. If the timeout is
	173	set too low under these conditions, it will appear that the remote host
174	is not reachable (which is almost the truth).
175
176	Reachability doesn't necessarily mean that the remote host is actually
177	functioning beyond its ability to echo packets. tcp is slightly better
178	at indicating the health of a system than icmp because it uses more of
179	the networking stack to respond.
180
181	Because of a lack of anything better, this module uses its own routines
182	to pack and unpack ICMP packets. It would be better for a separate
183	module to be written which understands all of the different kinds of
184	ICMP packets.
185
ddbbf559	186	AUTHORS
ddbbf559	187	Current maintainers:
505f3f16	188	colinm@cpan.org (Colin McMillen)
ddbbf559	189	bbb@cpan.org (Rob Brown)
505f3f16	190
	191	Stream protocol:
	192	bronson@trestle.com (Scott Bronson)
	193
	194	Original pingecho():
	195	karrer@bernina.ethz.ch (Andreas Karrer)
	196	pmarquess@bfsec.bt.co.uk (Paul Marquess)
	197
	198	Original Net::Ping author:
	199	mose@ns.ccsn.edu (Russell Mosemann)
	200
505f3f16	201	COPYRIGHT
ddbbf559	202	Copyright (c) 2001, Colin McMillen. All rights reserved.
	203
	204	Copyright (c) 2001, Rob Brown. All rights reserved.
505f3f16	205
	206	This program is free software; you may redistribute it and/or modify it
	207	under the same terms as Perl itself.
	208