NAME
POE::Component::Client::NNTP - A POE component that implements an RFC
3977 NNTP client.
VERSION
version 2.22
SYNOPSIS
# Connects to NNTP Server, selects a group, then downloads all current articles.
use strict;
use POE;
use POE::Component::Client::NNTP;
use Mail::Internet;
use FileHandle;
$|=1;
my $nntp = POE::Component::Client::NNTP->spawn ( 'NNTP-Client', { NNTPServer => 'news.host' } );
POE::Session->create(
package_states => [
'main' => { nntp_disconnected => '_shutdown',
nntp_socketerr => '_shutdown',
nntp_421 => '_shutdown',
nntp_200 => '_connected',
nntp_201 => '_connected',
},
'main' => [ qw(_start nntp_211 nntp_220 nntp_223 nntp_registered)
],
],
);
$poe_kernel->run();
exit 0;
sub _start {
my ($kernel,$heap) = @_[KERNEL,HEAP];
# Our session starts, register to receive all events from poco-client-nntp
$kernel->post ( 'NNTP-Client' => register => 'all' );
# Okay, ask it to connect to the server
$kernel->post ( 'NNTP-Client' => 'connect' );
undef;
}
sub nntp_registered {
my $nntp_object = $_[ARG0];
undef;
}
sub _connected {
my ($kernel,$heap,$text) = @_[KERNEL,HEAP,ARG0];
print "$text\n";
# Select a group to download from.
$kernel->post( 'NNTP-Client' => group => 'random.group' );
undef;
}
sub nntp_211 {
my ($kernel,$heap,$text) = @_[KERNEL,HEAP,ARG0];
print "$text\n";
# The NNTP server sets 'current article pointer' to first article in the group.
# Retrieve the first article
$kernel->post( 'NNTP-Client' => 'article' );
undef;
}
sub nntp_220 {
my ($kernel,$heap,$text,$article) = @_[KERNEL,HEAP,ARG0,ARG1];
print "$text\n";
my $message = Mail::Internet->new( $article );
my $filename = $message->head->get( 'Message-ID' );
my $fh = new FileHandle "> articles/$filename";
$message->print( $fh );
$fh->close;
# Set 'current article pointer' to the 'next' article in the group.
$kernel->post( 'NNTP-Client' => 'next' );
undef;
}
sub nntp_223 {
my ($kernel,$heap,$text) = @_[KERNEL,HEAP,ARG0];
print "$text\n";
# Server has moved to 'next' article. Retrieve it.
# If there isn't a 'next' article an 'nntp_421' is generated
# which will call '_shutdown'
$kernel->post( 'NNTP-Client' => 'article' );
undef;
}
sub _shutdown {
my ($kernel,$heap) = @_[KERNEL,HEAP];
# We got disconnected or a socketerr unregister and terminate the component.
$kernel->post ( 'NNTP-Client' => unregister => 'all' );
$kernel->post ( 'NNTP-Client' => 'shutdown' );
undef;
}
DESCRIPTION
POE::Component::Client::NNTP is a POE component that provides
non-blocking NNTP access to other components and sessions. NNTP is
described in RFC 3977 <http://www.faqs.org/rfcs/rfc3977.html>, please
read it before doing anything else.
In your component or session, you spawn a NNTP client component, assign
it an alias, and then send it a 'register' event to start receiving
responses from the component.
The component takes commands in the form of events and returns the
salient responses from the NNTP server.
CONSTRUCTOR
"spawn"
Takes two arguments, a kernel alias to christen the new component
with and a hashref.
Possible values for the hashref are:
'NNTPServer', the DNS name or IP address of the NNTP host to connect to;
'Port', the IP port on that host
'LocalAddr', an IP address on the client to connect from.
'UseSSL', set to a true value to indicate that the poco should use SSL
'TimeOut', number of seconds to wait for a response from server
If "NNTPServer" is not specified, the default is "news", unless the
environment variable "NNTPServer" is set. If "Port" is not specified
the default is 119.
POE::Component::Client::NNTP->spawn( 'NNTP-Client', { NNTPServer => 'news', Port => 119,
LocalAddr => '192.168.1.99' } );
"UseSSL" requires that POE::Component::SSLify is installed.
"TimeOut" is an optional number of seconds to wait between sending a
command to the server and receiving a response. If the timeout
occurs then the connection to the server is terminated and a
"nntp_disconnected" event is triggered. The default behaviour is not
to enable timeouts.
Returns a POE::Component::Client::NNTP object.
METHODS
"session_id"
Returns the session ID of the component's POE::Session.
"connected"
Indicates true or false as to whether the component is currently
connected to a server or not.
INPUT
The component accepts the following events:
"register"
Takes N arguments: a list of event names that your session wants to
listen for, minus the 'nntp_' prefix, ( this is similar to
POE::Component::IRC ).
Registering for "all" will cause it to send all NNTP-related events
to you; this is the easiest way to handle it.
"unregister"
Takes N arguments: a list of event names which you don't want to
receive. If you've previously done a "register" for a particular
event which you no longer care about, this event will tell the NNTP
connection to stop sending them to you. (If you haven't, it just
ignores you. No big deal).
"connect"
Takes no arguments. Tells the NNTP component to start up a
connection to the previously specified NNTP server. You will receive
a "nntp_connected" event.
"disconnect"
Takes no arguments. Terminates the socket connection ungracelessly.
"shutdown"
Takes no arguments. Terminates the component.
Always ensure that you call "unregister" before shutting down the
component.
The following are implemented NNTP commands, check RFC 3977
<http://www.faqs.org/rfcs/rfc3977.html> for the arguments accepted by
each. Arguments can be passed as a single scalar or a list of arguments:
"article"
Takes either a valid message-ID or a numeric-ID.
"body"
Takes either a valid message-ID or a numeric-ID.
"head"
Takes either a valid message-ID or a numeric-ID.
"stat"
Takes either a valid message-ID or a numeric-ID.
"group"
Takes the name of a newsgroup to select.
"help"
Takes no arguments.
"ihave"
Takes one argument, a message-ID.
"last"
Takes no arguments.
"list"
Takes no arguments.
"newgroups"
Can take up to four arguments: a date, a time, optionally you can
specify GMT and an optional list of distributions.
"newnews"
Can take up to five arguments: a newsgroup, a date, a time,
optionally you can specify GMT and an optional list of
distributions.
"next"
Takes no arguments.
"post"
Takes no arguments. Once you have sent this expect to receive an
'nntp_340' event. When you receive this send the component a
'send_post' event, see below.
"send_post"
Takes one argument, an array ref containing the message to be
posted, one line of the message to each array element.
"quit"
Takes no arguments.
"slave"
Takes no arguments.
"capabilities"
Returns a list of capabilities.
"listgroup"
Provides a list of article numbers in a group.
"date"
Find out the current Coordinated Universal Time
"over"
The OVER command returns the contents of all the fields in the
database for an article specified by message-id.
"hdr"
The HDR command provides access to specific fields from an article
specified by message-id.
"authinfo"
Takes two arguments: first argument is either "user" or "pass",
second argument is the user or password, respectively. Not
technically part of RFC 3977
<http://www.faqs.org/rfcs/rfc3977.html>, but covered in RFC 2980
<http://www.faqs.org/rfcs/rfc2980.html>.
"send_cmd"
The catch-all event :) Anything sent to this is passed directly to
the NNTP server. Use this to implement any non-RFC commands that you
want, or to completely bypass all the above if you so desire.
OUTPUT
The following events are generated by the component:
"nntp_registered"
Generated when you either explicitly "register" with the component
or you spawn a NNTP poco from within your own session. "ARG0" is the
poco's object.
"nntp_connected"
Generated when the component successfully makes a connection to the
NNTP server. Please note, that this is only the underlying network
connection. Wait for either an "nntp_200" or "nntp_201" before
sending any commands to the server.
"nntp_disconnected"
Generated when the link to the NNTP server is dropped for whatever
reason.
"nntp_socketerr"
Generated when the component fails to establish a connection to the
NNTP server.
"Numeric" responses ( See RFC 977 and RFC 2980 )
Messages generated by NNTP servers consist of a numeric code and a
text response. These will be sent to you as events with the numeric
code prefixed with "nntp_". "ARG0"is the text response.
Certain responses return following text, such as the "ARTICLE"
command, which returns the specified article. These responses are
returned in an array ref contained in "ARG1".
Eg.
$kernel->post( 'NNTP-Client' => article => $article_num );
sub nntp_220 {
my ($kernel,$heap,$text,$article) = @_[KERNEL,HEAP,ARG0,ARG1];
print "$text\n";
if ( scalar @{ $article } > 0 ) {
foreach my $line ( @{ $article } ) {
print STDOUT $line;
}
}
undef;
}
Possible nntp_ values are:
100 help text follows
199 debug output
200 server ready - posting allowed
201 server ready - no posting allowed
202 slave status noted
205 closing connection - goodbye!
211 n f l s group selected
215 list of newsgroups follows
220 n <a> article retrieved - head and body follow
221 n <a> article retrieved - head follows
222 n <a> article retrieved - body follows
223 n <a> article retrieved - request text separately
230 list of new articles by message-id follows
231 list of new newsgroups follows
235 article transferred ok
240 article posted ok
250 authentication accepted, successful authentication using the AUTHINFO command extension.
281 authentication accepted, successful authentication using the AUTHINFO command extension.
335 send article to be transferred. End with <CR-LF>.<CR-LF>
340 send article to be posted. End with <CR-LF>.<CR-LF>
381 more authentication information required, preliminary response to the AUTHINFO command extension.
400 service discontinued
411 no such news group
412 no newsgroup has been selected
420 no current article has been selected
421 no next article in this group
422 no previous article in this group
423 no such article number in this group
430 no such article found
435 article not wanted - do not send it
436 transfer failed - try again later
437 article rejected - do not try again.
440 posting not allowed
441 posting failed
500 command not recognized
501 command syntax error
502 access restriction or permission denied
503 program fault - command not performed
PLUGINS
POE::Component::Client::NNTP now utilises POE::Component::Pluggable to
enable a POE::Component::IRC type plugin system.
PLUGIN HANDLER TYPES
There are two types of handlers that can registered for by plugins,
these are
"NNTPSERVER"
These are the "nntp_" prefixed events that are generated. In a
handler arguments are passed as scalar refs so that you may mangle
the values if required.
"NNTPCMD"
These are generated whenever an nntp command is sent to the
component. Again, any arguments passed are scalar refs for
manglement.
PLUGIN EXIT CODES
Plugin handlers should return a particular value depending on what
action they wish to happen to the event. These values are available as
constants which you can use with the following line:
use POE::Component::Client::NNTP::Constants qw(:ALL);
The return values have the following significance:
"NNTP_EAT_NONE"
This means the event will continue to be processed by remaining
plugins and finally, sent to interested sessions that registered for
it.
"NNTP_EAT_CLIENT"
This means the event will continue to be processed by remaining
plugins but it will not be sent to any sessions that registered for
it. This means nothing will be sent out on the wire if it was an
NNTPCMD event, beware!
"NNTP_EAT_PLUGIN"
This means the event will not be processed by remaining plugins, it
will go straight to interested sessions.
"NNTP_EAT_ALL"
This means the event will be completely discarded, no plugin or
session will see it. This means nothing will be sent out on the wire
if it was an NNTPCMD event, beware!
PLUGIN METHODS
The following methods are available:
"pipeline"
Returns the POE::Component::Pluggable::Pipeline object.
"plugin_add"
Accepts two arguments:
The alias for the plugin
The actual plugin object
The alias is there for the user to refer to it, as it is possible to
have multiple plugins of the same kind active in one
POE::Component::Client::NNTP object.
This method goes through the pipeline's push() method.
This method will call $plugin->plugin_register( $nntp )
Returns the number of plugins now in the pipeline if plugin was
initialized, undef if not.
"plugin_del"
Accepts one argument:
The alias for the plugin or the plugin object itself
This method goes through the pipeline's remove() method.
This method will call $plugin->plugin_unregister( $irc )
Returns the plugin object if the plugin was removed, undef if not.
"plugin_get"
Accepts one argument:
The alias for the plugin
This method goes through the pipeline's get() method.
Returns the plugin object if it was found, undef if not.
"plugin_list"
Has no arguments.
Returns a hashref of plugin objects, keyed on alias, or an empty
list if there are no plugins loaded.
"plugin_order"
Has no arguments.
Returns an arrayref of plugin objects, in the order which they are
encountered in the pipeline.
"plugin_register"
Accepts the following arguments:
The plugin object
The type of the hook, NNTPSERVER or NNTPCMD
The event name(s) to watch
The event names can be as many as possible, or an arrayref. They
correspond to the prefixed events and naturally, arbitrary events
too.
You do not need to supply events with the prefix in front of them,
just the names.
It is possible to register for all events by specifying 'all' as an
event.
Returns 1 if everything checked out fine, undef if something's
seriously wrong
"plugin_unregister"
Accepts the following arguments:
The plugin object
The type of the hook, NNTPSERVER or NNTPCMD
The event name(s) to unwatch
The event names can be as many as possible, or an arrayref. They
correspond to the prefixed events and naturally, arbitrary events
too.
You do not need to supply events with the prefix in front of them,
just the names.
It is possible to register for all events by specifying 'all' as an
event.
Returns 1 if all the event name(s) was unregistered, undef if some
was not found.
PLUGIN TEMPLATE
The basic anatomy of a plugin is:
package Plugin;
# Import the constants, of course you could provide your own
# constants as long as they map correctly.
use POE::Component::NNTP::Constants qw( :ALL );
# Our constructor
sub new {
...
}
# Required entry point for plugins
sub plugin_register {
my( $self, $nntp ) = @_;
# Register events we are interested in
$nntp->plugin_register( $self, 'NNTPSERVER', qw(all) );
# Return success
return 1;
}
# Required exit point for pluggable
sub plugin_unregister {
my( $self, $nntp ) = @_;
# Pluggable will automatically unregister events for the plugin
# Do some cleanup...
# Return success
return 1;
}
sub _default {
my( $self, $nntp, $event ) = splice @_, 0, 3;
print "Default called for $event\n";
# Return an exit code
return NNTP_EAT_NONE;
}
CAVEATS
The group event sets the current working group on the server end. If you
want to use group and numeric form of article|head|etc then you will
have to spawn multiple instances of the component for each group you
want to access concurrently.
SEE ALSO
RFC 977 <http://www.faqs.org/rfcs/rfc977.html>
RFC 2980 <http://www.faqs.org/rfcs/rfc2980.html>
POE::Component::Pluggable
AUTHOR
Chris Williams <chris@bingosnet.co.uk>
COPYRIGHT AND LICENSE
This software is copyright (c) 2011 by Chris Williams and Dennis Taylor.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.