NAME¶
POE::Component::Client::Ping - a non-blocking ICMP ping client
SYNOPSIS¶
use POE qw(Component::Client::Ping);
POE::Component::Client::Ping->spawn(
Alias => "pingthing", # defaults to "pinger"
Timeout => 10, # defaults to 1 second
Retry => 3, # defaults to 1 attempt
OneReply => 1, # defaults to disabled
Parallelism => 64, # defaults to autodetect
BufferSize => 65536, # defaults to undef
AlwaysDecodeAddress => 1, # defaults to 0
);
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.
$retry, # Optional retries. It overrides the default.
);
}
# This is the sub which is called when the session receives a "pong"
# event. It handles responses from the Ping component.
sub got_pong {
my ($request, $response) = @_[ARG0, ARG1];
my ($req_address, $req_timeout, $req_time) = @$request;
my ($resp_address, $roundtrip_time, $resp_time, $resp_ttl) = @$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];
...;
}
DESCRIPTION¶
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 "spawn" method, not created anew with a "new" one.
PoCo::Client::Ping's "spawn" method takes a few named parameters:
- Alias => $session_alias
- "Alias" sets the component's alias. It is the
target of post() calls. See the synopsis. The alias defaults to
"pinger".
- Socket => $raw_socket
- "Socket" 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.
- Timeout => $ping_timeout
- "Timeout" sets the default amount of time (in
seconds) a Ping component will wait for a single ICMP echo reply before
retrying. It is 1 by default. It is 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.
- Retry => $ping_attempts
- "Retry" sets the default number of attempts a
ping will be sent before it should be considered failed. It is 1 by
default.
- OneReply => 0|1
- Set "OneReply" 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.
"OneReply" 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 "OneReply" is
enabled. This reply will represent either the first ICMP ECHO REPLY to
arrive or that the timeout period has ended.
- Parallelism => $limit
- Parallelism sets POE::Component::Client::Ping's maximum
number of simultaneous ICMP requests. Higher numbers speed up the
processing of large host lists, up to the point where the operating system
or network becomes oversaturated and begin to drop packets.
The difference can be dramatic. A tuned Parallelism can enable responses
down to 1ms, depending on the network, although it will take longer to get
through the hosts list.
Pinging 762 hosts at Parallelism=64
Starting to ping hosts.
Pinged 10.0.0.25 - Response from 10.0.0.25 in 0.002s
Pinged 10.0.0.200 - Response from 10.0.0.200 in 0.003s
Pinged 10.0.0.201 - Response from 10.0.0.201 in 0.001s
real 1m1.923s
user 0m2.584s
sys 0m0.207s
Responses will take significantly longer with an untuned Parallelism, but
the total run time will be quicker.
Pinging 762 hosts at Parallelism=500
Starting to ping hosts.
Pinged 10.0.0.25 - Response from 10.0.0.25 in 3.375s
Pinged 10.0.0.200 - Response from 10.0.0.200 in 1.258s
Pinged 10.0.0.201 - Response from 10.0.0.201 in 2.040s
real 0m13.410s
user 0m6.390s
sys 0m0.290s
Excessively high parallelism values may saturate the OS or network,
resulting in few or no responses.
Pinging 762 hosts at Parallelism=1000
Starting to ping hosts.
real 0m20.520s
user 0m7.896s
sys 0m0.297s
By default, POE::Component::Client::Ping will guess at an optimal
Parallelism value based on the raw socket receive buffer size and the
operating system's nominal ICMP packet size. The latter figure is 3000
octets for Linux and 100 octets for other systems. ICMP packets are
generally under 90 bytes, but operating systems may use alternative
numbers when calculating buffer capacities. The component tries to mimic
calculations observed in the wild.
When in doubt, experiment with different Parallelism values and use the one
that works best.
- BufferSize => $bytes
- If set, then the size of the receive buffer of the raw
socket will be modified to the given value. The default size of the
receive buffer is operating system dependent. If the buffer cannot be set
to the given value, a warning will be generated but the system will
continue working. Note that if the buffer is set too small and too many
ping replies arrive at the same time, then the operating system may
discard the ping replies and mistakenly cause this component to believe
the ping to have timed out. In this case, you will typically see discards
being noted in the counters displayed by 'netstat -s'.
Increased BufferSize values can expand the practical limit for
Parallelism.
- AlwaysDecodeAddress => 0|1
- If set, then any input addresses will always be looked up,
even if the hostname happens to be only 4 characters in size. Ideally, you
should be passing addresses in to the system to avoid slow hostname
lookups, but if you must use hostnames and there is a possibility that you
might have short hostnames, then you should set this.
- Payload => $bytes
- Sets the ICMP payload (data bytes). Otherwise the component
generates 56 data bytes internally. Note that some firewalls will discard
ICMP packets with nonstandard payload sizes.
Sessions communicate asynchronously with the Client::Ping component. They post
ping requests to it, and they receive pong events back.
Requests are posted to the component's "ping" handler. They include
the name of an event to post back, an address to ping, and an optional amount
of time to wait for responses. The address may be a numeric dotted quad, a
packed inet_aton address, or a host name. Host names are not recommended: they
must be looked up for every ping request, and DNS lookups can be very slow.
The optional timeout overrides the one set when "spawn" is called.
Ping responses come with two array references:
my ($request, $response) = @_[ARG0, ARG1];
$request contains information about the original request:
my (
$req_address, $req_timeout, $req_time, $req_user_args,
) = @$request;
- $req_address
- This is the original request address. It matches the
address posted along with the original "ping" request.
It is useful along with $req_user_args for pairing requests with their
corresponding responses.
- $req_timeout
- This is the original request timeout. It's either the one
passed with the "ping" request or the default timeout set with
"spawn".
- $req_time
- This is the time that the "ping" event was
received by the Ping component. It is a real number based on the current
system's time() epoch.
- $req_user_args
- This is a scalar containing arbitrary data that can be sent
along with a request. It's often used to provide continuity between
requests and their responses. $req_user_args may contain a reference to
some larger data structure.
To use it, replace the response event with an array reference in the
original request. The array reference should contain two items: the actual
response event and a scalar with the context data the program needs back.
See the SYNOPSIS for an example.
$response contains information about the ICMP ping response. There may be
multiple responses for a single request.
my ($response_address, $roundtrip_time, $reply_time, $reply_ttl) =
@$response;
- $response_address
- This is the address that responded to the ICMP echo
request. It may be different than $request_address, especially if the
request was sent to a broadcast address.
$response_address will be undefined if $request_timeout seconds have
elapsed. This marks the end of responses for a given request. Programs can
assume that no more responses will be sent for the request address. They
may use this marker to initiate another ping request.
- $roundtrip_time
- This is the number of seconds that elapsed between the ICMP
echo request's transmission and its corresponding response's receipt. It's
a real number. This is purely the trip time and does *not* include any
time spent queueing if the system's parallelism limit caused the ping
transmission to be delayed.
- $reply_time
- This is the time when the ICMP echo response was received.
It is a real number based on the current system's time()
epoch.
- $reply_ttl
- This is the ttl for the echo response packet we
received.
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, RES_TTL
SEE ALSO¶
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.
BUG TRACKER¶
https://rt.cpan.org/Dist/Display.html?Queue=POE-Component-Client-Ping
REPOSITORY¶
http://github.com/rcaputo/poe-component-client-ping/
OTHER RESOURCES¶
http://search.cpan.org/dist/POE-Component-Client-Ping/
AUTHOR & COPYRIGHTS¶
POE::Component::Client::Ping is Copyright 1999-2009 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.
You can learn more about POE at
http://poe.perl.org/