POE::Component::Client::Ping - a non-blocking ICMP ping client

  use POE qw(Component::Client::Ping);

  POE::Component::Client::Ping->spawn(
    Alias     => "pingthing",  # defaults to "pinger"
    Timeout   => 10,           # defaults to 1 second
    OneReply  => 1             # defaults to disabled
  );

  sub some_event_handler {
    $kernel->post(
      "pingthing", # Post the request to the "pingthing" component.
      "ping",      # Ask it to "ping" an address.
      "pong",      # Have it post an answer as a "pong" event.
      $address,    # This is the address we want to ping.
      $timeout,    # Optional timeout.  It overrides the default.
    );
  }

  # This is the sub which is called when the session receives a "pong"
  # event.  It handles responses from the Ping component.
  sub got_pong {
    my ($request, $response) = @_[ARG0, ARG1];

    my ($req_address, $req_timeout, $req_time)      = @$request;
    my ($resp_address, $roundtrip_time, $resp_time) = @$response;

    # The response address is defined if this is a response.
    if (defined $resp_address) {
      printf(
        "ping to %-15.15s at %10d. pong from %-15.15s in %6.3f s\n",
        $req_address, $req_time,
        $resp_address, $roundtrip_time,
      );
      return;
    }

    # Otherwise the timeout period has ended.
    printf(
      "ping to %-15.15s is done.\n", $req_address,
    );
  }

  or

  use POE::Component::Client::Ping ":const";

  # Post an array ref as the callback to get data back to you
  $kernel->post("pinger", "ping", [ "pong", $user_data ]);

  # use the REQ_USER_ARGS constant to get to your data
  sub got_pong {
      my ($request, $response) = @_[ARG0, ARG1];
      my $user_data = $request->[REQ_USER_ARGS];
      ...;
  }

POE::Component::Client::Ping is non-blocking ICMP ping client. It lets several other sessions ping through it in parallel, and it lets them continue doing other things while they wait for responses.

Ping client components are not proper objects. Instead of being created, as most objects are, they are spawned as separate sessions. To avoid confusion (and hopefully not cause other confusion), they must be spawned with a CWspawn method, not created anew with a CWnew one.

PoCo::Client::Ping's CWspawn method takes a few named parameters: CWAlias sets the component's alias. It is the target of post() calls. See the synopsis. The alias defaults to pinger. CWSocket allows developers to open an existing raw socket rather than letting the component attempt opening one itself. If omitted, the component will create its own raw socket. This is useful for people who would rather not perform a security audit on POE, since it allows them to create a raw socket in their own code and then run POE at reduced privileges. CWTimeout sets the default amount of time a Ping component will wait for an ICMP echo reply, in seconds. It is 1 by default. It's possible and meaningful to set the timeout to a fractional number of seconds. This default timeout is only used for ping requests that don't include their own timeouts.

OneReply => 0|1

Set CWOneReply to prevent the Ping component from waiting the full timeout period for replies. Normally the ICMP protocol allows for multiple replies to a single request, so it's proper to wait for late responses. This option disables the wait, ending the ping transaction at the first response. Any subsequent responses will be silently ignored. CWOneReply is disabled by default, and a single successful request will generate at least two responses. The first response is a successful ICMP ECHO REPLY event. The second is an undefined response event, signifying that the timeout period has ended. A ping request will generate exactly one reply when CWOneReply is enabled. This reply will represent either the first ICMP ECHO REPLY to arrive or that the timeout period has ended.

Sessions communicate asynchronously with the Client::Ping component. They post ping requests to it, and they receive pong events back.

Requests are posted to the component's ping handler. They include the name of an event to post back, an address to ping, and an optional amount of time to wait for responses. The address may be a numeric dotted quad, a packed inet_aton address, or a host name. Host names are not recommended: they must be looked up for every ping request, and DNS lookups can be very slow. The optional timeout overrides the one set when CWspawn is called.

Ping responses come with two array references:

  my ($request, $response) = @_[ARG0, ARG1];

CW$request contains information about the original request:

  my (
    $req_address, $req_timeout, $req_time, $req_user_args,
  ) = @$request;

CW$response contains information about the ICMP ping response. There may be multiple responses for a single request.

  my ($response_address, $roundtrip_time, $reply_time) = @$response;

If the :const tagset is imported the following constants will be exported:

REQ_ADDRESS, REQ_TIMEOUT, REQ_TIME REQ_USER_ARGS, RES_ADDRESS, RES_ROUNDTRIP, RES_TIME

This component's ICMP ping code was lifted from Net::Ping, which is an excellent module when you only need to ping one host at a time.

See POE, of course, which includes a lot of documentation about how POE works.

Also see the test program, t/01_ping.t, in the component's distribution.

None currently known.

POE::Component::Client::Ping is Copyright 1999-2004 by Rocco Caputo. All rights are reserved. POE::Component::Client::Ping is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

Rocco may be contacted by e-mail via <rcaputo@cpan.org>.

You can learn more about POE at <http://poe.perl.org/>.