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From: [email protected] (Russell Mosemann)
Newsgroups: comp.lang.perl.announce,comp.lang.perl.misc
Subject: [ANNOUNCE] Net::Ping 2.02 released
Followup-To: comp.lang.perl.misc
Date: 27 Sep 1996 03:01:46 GMT
Organization: Concordia College, Seward, NE
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  Version 2.02 of Net::Ping has been uploaded to the CPAN archives
and should be available shortly.  This new version has been rewritten
to be object oriented and includes the original tcp ping, a udp ping
and a "real" icmp ping.  The man page follows.


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");
    foreach $host (@host_array)
    {
        print "$host is ";
        print "NOT " unless $p->ping($host, 2);
        print "reachable.\n";
        sleep(1);
    }
    $p->close();

    $p = Net::Ping->new("tcp", 2);
    while ($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 three different protocols to use for
    the ping.  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.

    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.

    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.

    $p->ping($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->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 tcp and udp protocols do
    not require special privileges, but not all network devices
    implement the echo protocol for tcp or udp.

    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.

    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.

--
Russell Mosemann     Concordia College      Voice: (402) 643-7445
Computing Center     Seward, NE 68434       Fax:   (402) 643-4073
"Look before you leap."  "He who hesitates is lost."

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