NAME¶
POE::Component::Client::TCP - a simplified TCP client
SYNOPSIS¶
#!perl
use warnings;
use strict;
use POE qw(Component::Client::TCP);
POE::Component::Client::TCP->new(
RemoteAddress => "yahoo.com",
RemotePort => 80,
Connected => sub {
$_[HEAP]{server}->put("HEAD /");
},
ServerInput => sub {
my $input = $_[ARG0];
print "from server: $input\n";
},
);
POE::Kernel->run();
exit;
DESCRIPTION¶
POE::Component::Client::TCP implements a generic single-Session client.
Internally it uses POE::Wheel::SocketFactory to establish the connection and
POE::Wheel::ReadWrite to interact with the server.
POE::Component::Client::TCP is customized by providing callbacks for common
operations. Most operations have sensible default callbacks, so clients may be
created with as little work as possible.
POE::Component::Client::TCP's ease of use comes at a price. The component is
generic, so it's not tuned to perform well for any particular application.
If performance is your primary goal, POE::Kernel's
select_read() and
select_write() perform about the same as IO::Select, but your code will
be portable across every event loop POE supports.
PUBLIC METHODS¶
new¶
new() starts a client based on POE::Component::Client::TCP and returns
the ID of the session that will handle server interaction.
new() returns immediately, which may be before the client has established
its connection. It is always reliable to wait for the "Connected"
callback to fire before transmitting data to the server.
The client's constructor may seem to take a daunting number of parameters. As
with most POE modules, POE::Component::Client::TCP tries to do as much work in
its constructor so that the run-time code path is relatively light.
Constructor Parameters Affecting the Session
The parameters in this section affect how the client's POE::Session object will
be created.
Alias
"Alias" is an optional symbolic name for the client's Session. It
allows other sessions to post events to the client, such as
"shutdown" and "reconnect". The client itself may
yield() these events, so an alias isn't usually needed.
Alias => "client",
Args
"Args" is optional. When specified, it holds an ARRAYREF that will be
passed to the "Started" callback via @_[ARG0..$#_]. This allows a
program to pass extra information into the client session.
InlineStates
"InlineStates" is optional. If specified, it must hold a hashref of
named callbacks. Its syntax is that of POE:Session->
create()'s
inline_states parameter.
ObjectStates
If "ObjectStates" is specified, it must hold an arrayref of objects
and the events they will handle. The arrayref must follow the syntax for
POE::Session->
create()'s object_states parameter.
PackageStates
When the optional "PackageStates" is set, it must hold an arrayref of
package names and the events they will handle The arrayref must follow the
syntax for POE::Session->
create()'s package_states parameter.
PreConnect
"PreConnect" is called before "Connected", and it has
different parameters: $_[ARG0] contains a copy of the socket before it's given
to POE::Wheel::ReadWrite for management. Most HEAP members are set, except of
course $_[HEAP]{server}, because the POE::Wheel::ReadWrite object has not been
created yet. "PreConnect" may enable SSL on the socket using
POE::Component::SSLify. "PreConnect" must return a valid socket to
complete the connection; the client will disconnect if anything else is
returned.
PreConnect => {
# Convert the socket into an SSL socket.
my $socket = eval { Client_SSLify($_[ARG0]) };
# Disconnect if SSL failed.
return if $@;
# Return the SSL-ified socket.
return $socket;
}
SessionType
Each client is created within its own Session. "SessionType" names the
class that will be used to create the session.
SessionType => "POE::Session::MultiDispatch",
"SessionType" is optional. The component will use
"POE::Session" by default.
SessionParams
"SessionParams" specifies additional parameters that will be passed to
the "SessionType" constructor at creation time. It must be an array
reference.
SessionParams => [ options => { debug => 1, trace => 1 } ],
Note: POE::Component::Client::TCP supplies its own POE::Session constructor
parameters. Conflicts between them and "SessionParams" may cause the
component to behave erratically. To avoid such problems, please limit
SessionParams to the "options" hash. See POE::Session for an known
options.
We may enable other options later. Please let us know if you need something.
Started
"Started" sets an optional callback that will be invoked within the
client session has been started. The callback's parameters are the usual for
the session's _start handler.
"Args" may be used to pass additional parameters to
"Started". This can be used to bypass issues introduced by closures.
The values from "Args" will be included in the @_[ARG0..$#_]
parameters.
sub handle_started {
my @args = @_[ARG0..$#_];
# ...
}
POE::Wheel::SocketFactory Constructor Parameters
The constructor parameters in this section affect how the client's
POE::Wheel::SocketFactory object will be created.
BindAddress
"BindAddress" specifies the local interface address to bind to before
starting to connect. This allows the client to connect from a specific address
when multiple interfaces are available.
"BindAddress" is optional. If specified, its value will be passed
directly to POE::Wheel::SocketFactory's BindAddress constructor parameter.
BindPort
"BindPort" sets the local socket port that the client will be bound to
before starting to connect. This allows the client to connect from a specific
port.
It's not usually necessary to bind to a particular port, so "BindPort"
is optional and disabled by default.
If specified, the value in "BindPort" is passed directly to
POE::Wheel::SocketFactory's own BindPort constructor parameter.
ConnectError
"ConnectError" is an optional callback to handle errors from
POE::Wheel::SocketFactory. These errors happen when a socket can't be created
or has trouble connecting to the remote host.
The following parameters will be passed to the callback along with the usual POE
event parameters: $_[ARG0] will describe what was happening at the time of
failure. $_[ARG1] and $_[ARG2] will contain the numeric and string versions of
$!, respectively.
Depending on the nature of the error and the type of client, it may be useful to
reconnect from the ConnectError callback.
ConnectError => sub {
my ($operation, $error_number, $error_string) = @_[ARG0..ARG2];
warn "$operation error $error_number occurred: $error_string";
if (error_is_recoverable($error_number)) {
$_[KERNEL]->delay( reconnect => 60 );
}
else {
$_[KERNEL]->yield("shutdown");
}
},
POE::Component::Client::TCP will shut down after ConnectError if a reconnect
isn't requested.
Connected
Connections are asynchronously set up and may take some time to complete.
"Connected" is an optional callback that notifies a program when the
connection has finally been made.
This is an advisory callback that occurs after a POE::Wheel::ReadWrite object
has already been created. Programs should not need to create their own.
"Connected" is called in response to POE::Wheel::SocketFactory's
SuccessEvent. In addition to the usual POE event parameters, it includes a
copy of the established socket handle in $_[ARG0]. POE::Component::Client::TCP
will manage the socket, so an application should rarely need to save a copy of
it. $_[ARG1] and $_[ARG2] contain the remote address and port as returned from
getpeername().
Connected => {
my ($socket, $peer_addr, $peer_port) = @_[ARG0, ARG1, ARG2];
# ...
}
See "PreConnect" to modify the socket before it's given to
POE::Wheel::ReadWrite.
ConnectTimeout
"ConnectTimeout" is the maximum number of seconds to wait for a
connection to be established. If it is omitted, Client::TCP relies on the
operating system to abort stalled
connect() calls.
The application will be notified of a timeout via the ConnectError callback. In
the case of a timeout, $_[ARG0] will contain "connect", and $_[ARG1]
and $_[ARG2] will contain the numeric and string representations of the
ETIMEDOUT error.
Domain
"Domain" sets the address or protocol family within which to operate.
The "Domain" may be any value that POE::Wheel::SocketFactory
supports. AF_INET (Internet address space) is used by default.
Use AF_INET6 for IPv6 support. This constant is exported by Socket. Also be sure
to have Socket::GetAddrInfo installed, which is required by
POE::Wheel::SocketFactory for IPv6 support.
RemoteAddress
"RemoteAddress" contains the address of the server to connect to. It
is required and may contain a host name ("poe.perl.org"), a dot- or
colon-separated numeric address (depending on the Domain), or a packed socket
address. Pretty much anything POE::Wheel::SocketFactory's RemoteAddress
parameter does.
RemotePort
"RemotePort" contains the port of the server to connect to. It is
required and may be a service name ("echo") or number (7).
POE::Wheel::ReadWrite Constructor Parameters
Parameters in this section control configuration of the client's
POE::Wheel::ReadWrite object.
Disconnected
"Disconnected" is an optional callback to notify a program that an
established socket has been disconnected. It includes no special parameters.
It may be useful to reconnect from the Disconnected callback, in the case of MUD
bots or long-running services. For example:
Disconnected => sub {
$_[KERNEL]->delay( reconnect => 60 );
},
The component will shut down if the connection ceases without being reconnected.
Filter
"Filter" specifies the type of POE::Filter object that will parse
input from and serialize output to a server. It may either be a scalar, an
array reference, or a POE::Filter object.
If "Filter" is a scalar, it will be expected to contain a POE::Filter
class name:
Filter => "POE::Filter::Line",
"Filter" is optional. In most cases, the default
"POE::Filter::Line" is fine.
If "Filter" is an array reference, the first item in the array will be
treated as a POE::Filter class name. The remaining items will be passed to the
filter's constructor. In this example, the vertical bar will be used as
POE::Filter::Line's record terminator:
Filter => [ "POE::Filter::Line", Literal => "|" ],
If it is an object, it will be cloned every time the client connects:
Filter => POE::Filter::Line->new(Literal => "|"),
Be sure to "use" the appropriate POE::Filter subclass when specifying
a "Filter" other than the default.
ServerError
"ServerError" is an optional callback that will be invoked when an
established server connection has encountered some kind of error. It is
triggered by POE::Wheel::ReadWrite's ErrorEvent. By default, the component
will log any errors to STDERR. This may be suppressed by defining a quieter
ServerError callback.
As with "ConnectError", it is invoked with the customary error
parameters: $_[ARG0] will contain the name of the operation that failed.
$_[ARG1] and $_[ARG2] will hold the numeric and string forms of $!,
respectively.
Components usually disconnect on error. POE::Component::Client::TCP will shut
down if the socket disconnects without being reconnected.
ServerFlushed
"ServerFlushed" is an optional callback to notify a program that
ReadWrite's output buffers have completely flushed. It has no special
parameters.
The component will shut down after a server flush if $heap->{shutdown} is
set.
ServerInput
"ServerInput" is a required callback. It is called for each fully
parsed input record received by POE::Wheel::ReadWrite. $_[ARG0] contains the
input record, the format of which is determined by the "Filter"
constructor parameter.
"SeverInput" will stop being called when $_[HEAP]{shutdown} is true.
The most reliable way to set the "shutdown" member is to call
$_[KERNEL]->yield("shutdown").
Public Events¶
POE::Component::Client::TCP handles a small number of public "command"
messages. These may be posted into the client from an external session, or
yielded from within the client.
connect¶
The "connect" event causes POE::Component::Client::TCP to begin
connecting to a server. It optionally includes a new RemoteHost and
RemotePort, both of which will be used for subsequent reconnections.
$_[KERNEL]->post(alias => connect => "127.0.0.1", 80);
If the client is already connected to a server, it will disconnect immediately
before beginning the new connection procedure. Buffered input and output will
be lost.
reconnect¶
The "reconnect" command causes POE::Component::Client::TCP to
immediately disconnect its current connection and begin reconnecting to its
most recently set RemoteHost and RemotePort. Any buffered input and output
will be lost.
shutdown¶
The "shutdown" command tells POE::Component::Client::TCP to flush its
buffers, disconnect, and begin DESTROY procedures.
All input will be discarded after receipt of "shutdown". All pending
output will be written to the server socket before disconnecting and
destructing.
Reserved Heap Members¶
POE::Component::Client::TCP requires some heap space for its own bookkeeping.
The following members are used and should be used as directed, or with care.
This sample input handler is an example of most reserved heap members:
sub handle_input {
# Pending input from when we were connected.
return unless $_[HEAP]{connected};
# We've been shut down.
return if $_[HEAP]{shutdown};
my $input = $_[ARG0];
$_[HEAP]{server}->put("you sent: $input");
}
server¶
The read-only "server" heap member contains the POE::Wheel object used
to connect to or talk with the server. While the component is connecting,
"server" will be a POE::Wheel::SocketFactory object. After the
connection has been made, "server" is replaced with a
POE::Wheel::ReadWrite object.
The most reliable way to avoid prematurely using "server" is to first
check the "connected" reserved heap member. See the example above.
shutdown¶
"shutdown" is a read-only flag that tells the component it's shutting
down. It should only be by the "shutdown" event, which does other
cleanup.
"shutdown" may be checked to avoid starting new work during a client's
shutting-down procedure. See the example above.
connected¶
"connected" is a read-only flag that indicates whether the component
is currently connected.
shutdown_on_error¶
"shutdown_on_error" is a read-only flag that governs the component's
shutdown-on-error behavior. When true, POE::Component::Client::TCP will
automatically shutdown when it encounters an error.
SEE ALSO¶
The SEE ALSO section in POE contains a table of contents covering the entire POE
distribution.
POE::Component::Server::TCP is the server-side counterpart to this module.
This component uses and exposes features from POE::Filter,
POE::Wheel::SocketFactory, and POE::Wheel::ReadWrite.
See "SYNOPSIS" in POE::Wheel::SocketFactory for a more efficient but
lower-level way to create clients and servers.
CAVEATS¶
This looks nothing like what Ann envisioned.
POE::Component::Client::TCP is a generic client. As such, it's not tuned for any
particular task. While it handles the common cases well and with a minimum of
code, it may not be suitable for everything.
AUTHORS & COPYRIGHTS¶
POE::Component::Client::TCP is Copyright 2001-2013 by Rocco Caputo. All rights
are reserved. POE::Component::Client::TCP is free software, and it may be
redistributed and/or modified under the same terms as Perl itself.
POE::Component::Client::TCP is based on code, used with permission, from Ann
Barcomb <kudra@domaintje.com>.
POE::Component::Client::TCP is based on code, used with permission, from Jos
Boumans <kane@cpan.org>.