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Edit: /usr/share/doc/perl-Net-Ping/README (21473B)

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("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);

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 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.

Functions
    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 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
        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 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 } );
        With 1 causes this module to use Time::HiRes module, allowing
        milliseconds to be returned by subsequent calls to ping().

$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 *NYI*
        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 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.

The bind() call can be omitted when specifying the "bind" option to
        new().

$p->message_type([$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 new().

$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, 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->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).

$p->port_number([$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"'

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 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.

INSTALL
    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.

BUGS
    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>

AUTHORS
      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)

This program is free software; you may redistribute it and/or modify it
    under the same terms as Perl itself.

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