Ubuntu Manpage: POE::Filter::HTTPD - parse simple HTTP requests, and serialize HTTP::Response

name
synopsis
description
public filter methods
caveats
streaming media
see also
bugs
authors & copyrights

NAME

       POE::Filter::HTTPD - parse simple HTTP requests, and serialize HTTP::Response

SYNOPSIS

         #!perl

         use warnings;
         use strict;

         use POE qw(Component::Server::TCP Filter::HTTPD);
         use HTTP::Response;

         POE::Component::Server::TCP->new(
           Port         => 8088,
           ClientFilter => 'POE::Filter::HTTPD',  ### <-- HERE WE ARE!

           ClientInput => sub {
             my $request = $_[ARG0];

             # It's a response for the client if there was a problem.
             if ($request->isa("HTTP::Response")) {
               my $response = $request;

               $request = $response->request;
               warn "ERROR: ", $request->message if $request;

               $_[HEAP]{client}->put($response);
               $_[KERNEL]->yield("shutdown");
               return;
             }

             my $request_fields = '';
             $request->headers()->scan(
               sub {
                 my ($header, $value) = @_;
                 $request_fields .= (
                   "<tr><td>$header</td><td>$value</td></tr>"
                 );
               }
             );

             my $response = HTTP::Response->new(200);
             $response->push_header( 'Content-type', 'text/html' );
             $response->content(
               "<html><head><title>Your Request</title></head>" .
               "<body>Details about your request:" .
               "<table border='1'>$request_fields</table>" .
               "</body></html>"
             );

             $_[HEAP]{client}->put($response);
             $_[KERNEL]->yield("shutdown");
           }
         );

         print "Aim your browser at port 8088 of this host.\n";
         POE::Kernel->run();
         exit;

DESCRIPTION

       POE::Filter::HTTPD interprets input streams as HTTP 0.9, 1.0 or 1.1 requests.  It returns a HTTP::Request
       objects upon successfully parsing a request.

       On failure, it returns an HTTP::Response object describing the failure.  The intention is that
       application code will notice the HTTP::Response and send it back without further processing. The
       erroneous request object is sometimes available via the "$r->request" in HTTP::Response method.  This is
       illustrated in the "SYNOPSIS".

       For output, POE::Filter::HTTPD accepts HTTP::Response objects and returns their corresponding streams.

       Please see HTTP::Request and HTTP::Response for details about how to use these objects.

PUBLIC FILTER METHODS

       POE::Filter::HTTPD implements the basic POE::Filter interface.

CAVEATS

Some versions of libwww are known to generate invalid HTTP. For example, this code (adapted from the
HTTP::Request::Common documentation) will cause an error in a POE::Filter::HTTPD daemon:

NOTE: Using this test with libwww-perl/5.834 showed that it added the proper HTTP/1.1 data! We're not
sure which version of LWP fixed this. This example is valid for older LWP installations, beware!

use HTTP::Request::Common;
use LWP::UserAgent;

my $ua = LWP::UserAgent->new();
$ua->request(POST 'http://example.com', [ foo => 'bar' ]);

By default, HTTP::Request is HTTP version agnostic. It makes no attempt to add an HTTP version header
unless you specifically declare a protocol using "$request->protocol('HTTP/1.0')".

According to the HTTP 1.0 RFC (1945), when faced with no HTTP version header, the parser is to default to
HTTP/0.9. POE::Filter::HTTPD follows this convention. In the transaction detailed above, the
Filter::HTTPD based daemon will return a 400 error since POST is not a valid HTTP/0.9 request type.

Upon handling a request error, it is most expedient and reliable to respond with the error and shut down
the connection. Invalid HTTP requests may corrupt the request stream. For example, the absence of a
Content-Length header signals that a request has no content. Requests with content but not that header
will be broken into a content-less request and invalid data. The invalid data may also appear to be a
request! Hilarity will ensue, possibly repeatedly, until the filter can find the next valid request. By
shutting down the connection on the first sign of error, the client can retry its request with a clean
connection and filter.

Streaming Media

       It is possible to use POE::Filter::HTTPD for streaming content, but an application can use it to send
       headers and then switch to POE::Filter::Stream.

       From the input handler (the InputEvent handler if you're using wheels, or the ClientInput handler for
       POE::Component::Server::TCP):

         my $response = HTTP::Response->new(200);
         $response->push_header('Content-type', 'audio/x-mpeg');
         $_[HEAP]{client}->put($response);
         $_[HEAP]{client}->set_output_filter(POE::Filter::Stream->new());

       Then the output-flushed handler (FlushEvent for POE::Wheel::ReadWrite, or ClientFlushed for
       POE::Component::Server::TCP) can put() chunks of the stream as needed.

         my $bytes_read = sysread(
           $_[HEAP]{file_to_stream}, my $buffer = '', 4096
         );

         if ($bytes_read) {
           $_[HEAP]{client}->put($buffer);
         }
         else {
           delete $_[HEAP]{file_to_stream};
           $_[KERNEL]->yield("shutdown");
         }

BUGS

       Many aspects of HTTP 1.0 and higher are not supported, such as keep-alive.  A simple I/O filter can't
       support keep-alive, for example.  A number of more feature-rich POE HTTP servers are on the CPAN.  See
       <http://search.cpan.org/search?query=POE+http+server&mode=dist>

AUTHORS & COPYRIGHTS

       POE::Filter::HTTPD was contributed by Artur Bergman.  Documentation is provided by Rocco Caputo.

       Please see POE for more information about authors and contributors.