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Perl Cookbook by Nathan Torkington, Tom Christiansen

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Debugging the Raw HTTP Exchange

Problem

Your CGI script is misbehaving strangely with your browser, and you suspect something in the HTTP header is missing. You want to find out exactly what your browser is sending to the server in the HTTP header.

Solution

Create your own fake web server, and point your browser at it, as shown in Example 19.6.

Example 19-6. dummyhttpd

#!/usr/bin/perl -w
# dummyhttpd - start an HTTP daemon and print what the client sends

use strict;
use HTTP::Daemon;  # need LWP-5.32 or better

my $server = HTTP::Daemon->new(Timeout => 60, LocalPort => 8989);
print "Please contact me at: <URL:", $server->url, ">\n";

while (my $client = $server->accept) {
  CONNECTION:
    while (my $answer = $client->get_request) {
        print $answer->as_string;
        $client->autoflush;
      RESPONSE:
        while (<STDIN>) {
            last RESPONSE   if $_ eq ".\n";
            last CONNECTION if $_ eq "..\n";
            print $client $_;
        }
        print "\nEOF\n";
    }
    print "CLOSE: ", $client->reason, "\n";
    $client->close;
    undef $client;
}

Discussion

It’s hard to keep track of which versions of all the different browsers still have which bugs. The fake server program can save you days of head scratching, because sometimes a misbehaving browser doesn’t send the server the right thing. Historically, we have seen aberrant browsers lose their cookies, mis-escape a URL, send the wrong status line, and do other even less obvious things.

To use the fake server, it’s best to run it on the same machine as the real server. That way your browser will still send it ...

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