#!/usr/bin/perl -w
#-------------------------------------------------------
# HTTP Debugger
#
# Copyright (c) 1999 John Nolan. All rights reserved. 
# This program is free software.  You may modify and/or 
# distribute it under the same terms as Perl itself.  
# This copyright notice must remain attached to the file.  
#
# You can run this file through either pod2man or pod2html 
# to produce pretty documentation in manual or html file format 
# (these utilities are part of the Perl 5 distribution).
#-------------------------------------------------------


=head1  NAME

B<httpdebug> - A tool for debugging HTTP transactions

=head1 SYNOPSIS

   httpdebug [-p port] [-t timeout]

=head1 README

This is a tool to help you debug HTTP transactions.  It uses both 
the HTTP server and HTTP client functionalities of the LWP bundle.  
Using this script, you can easily and quickly mimic and tweak transactions 
between servers and clients.  You operate this program using a Web browser. 

=head1 DESCRIPTION

When you launch this program from the command line, it becomes 
a tiny HTTP daemon.  For example, if you launch this program with
the parameter "-p 8080", then it will become a Web server 
on port 8080.  You can then access it using a browser at the URL 
"http://host.domain.com:8080/c".  The page that you will
see is a control panel for the program.  

With any other URL besides "/c" (and a few other paths),
this little server will only print out a brief test page (i.e.,
test headers and a test document). From the control panel, 
you can specifically adjust the test headers and the test document 
that the server (this program) sends to the client (something else), 
and then watch how the client responds.  

All transactions are logged, and you can view these 
transaction logs right from the browser, by using
the path "/l" or "/log". 

You can use the debugger's HTTP client functionality to interact with 
a remote web server.  From the control panel, you can specify a URL,
and the debugger (as HTTP client) will send that request to a remote
Web server and save the response headers and document. 
If you want, you can manually adjust the header data and
request lines that the HTTP client uses during this transaction.

After fetching a document like this, the debugger's server functionality 
can immediately use this information to mimic that remote server.  
In this way, you can very easily simulate the interactions between 
a remote server and a remote client, by just making your little server 
behave exactly like the remote server.

You can very carefully tweak the headers and document data 
that you are sending and receiving.  This can be useful for 
locating otherwise obscure errors. 

The debugger has a built-in timeout, which by default is 180 seconds.
This helps prevent you from launching the HTTP daemon and then
forgetting that it's running, which could be a security issue. 
When you launch the program from the command line, use the -t option
to specify a timeout (in seconds).  The program will exit
after that number of seconds of idle time. 

=head1 The Log page

The debugger has a log page, where it records the data transferred
(both headers and data) during HTTP transactions. On the log page, 
this is the color scheme:

	Remote client: blue italics
	Local server: black italics
	Local client: black roman
	Remote server: green roman

Headers and data are all the same color.  They are separated
by two newlines, of course. 

The debugger does not log transactions made when it
serves up the control panel, the log page, nor this help page.

=head1 Special URLs

Below is a list of all the URLs that are "special" for this 
Web server:

    Control panel: /c  /con /cons /console /control
    Log page:      /l  /log
    Help page:     /i  /info /h /help /q

Any other URLs will result in the sending of the test page
as a response. 

=head1 Do I really need this thing?

Maybe not.  You can do practically all of these things
from the command line using netcat.  But it's a lot
trickier that way, especially if you are not a die-hard
command-line jockey.  This interface is certainly faster,
and it keeps a nice handy log of all transactions. 
Plus it has pretty colors.  

=head1 SCRIPT CATEGORIES

Web
CGI

=head1 PREREQUISITES

You basically need the LWP bundle and CGI.pm. If your version of
CGI.pm does not have the noDebug pragma, then consider downloading
a later version of CGI.pm from CPAN. 

=head1 AUTHOR 

John Nolan  jpnolan@sonic.net  February 1999.  

=cut


#-------------------------------------------------------

use CGI qw(:standard :noDebug);
use HTTP::Daemon;
use HTTP::Status;
use HTTP::Request;
use LWP::UserAgent;
use Getopt::Std;
use Sys::Hostname;

use strict;

use vars qw( $opt_p $opt_t $Progname $nontext $menubar );

$|++;

# NOTE: Near the end of this program is a BEGIN block
# where some important variables are initialized. 
# It's at the end of the program, rather than up here,
# only because it's really long. 

getopts('p:t:');


#----------------------------------------------
# Setup Global variables
#
my $PORT      = (defined $opt_p ? $opt_p :    0 );
my $TIMEOUT   = (defined $opt_t ? $opt_t :  180 );

# NOTE: hostname() does not return the FQDN, only the hostname.  
# You may want to just hard-code your hostname here, instead.
#
my $HOST      = hostname();   
chomp($HOST);

my $req_counter = 1;
my $res_counter = 1;

my $d = new HTTP::Daemon (LocalAddr => $HOST);
$d    = new HTTP::Daemon (LocalAddr => $HOST, LocalPort => $PORT) if $PORT;

unless (defined $d) {
	warn "Could not bind to port.  I'm going to have to exit.  Sorry.\n";
	exit(-1);
}

my $url       = $d->url;

my @helpinfo  = <DATA>;             # Read the info at end of code

my $log       = "";                 # Where we store transaction logs
my $delim     = ('-') x 60 . "\n";  # Delimiter for displaying logs
my $agentname = "Mozilla (compatible: LWP $LWP::VERSION)";

my %res_headers;               # Hash will hold response headers that we serve
my %res_content;               # Hash will hold response content that we serve
my %request;                   # Hash will hold request data that we send

$res_headers{'current'} = ($res_headers{'HTML'} or "");
$res_content{'current'} = ($res_content{'HTML'} or "<H1>Oops -- test no data!</H1>");

$request{'current'} = "GET http://www.perl.org HTTP/1.1\nUser-Agent: $agentname\n\n";



#----------------------------------------------
# Escape HTML so we can display raw HTML in a web browser
#
sub escapeHTML {

	my %ENTITIES = (

		'&' => '&amp;',
		'>' => '&gt;',
		'<' => '&lt;',
		'"' => '&quot;',
	);

	my $text = shift;
	$text =~ s/([&\"><])/$ENTITIES{$1}/ge;
	return $text;
}

#----------------------------------------------
# Create a Web browser and fetch a URL, headers and all.
# If necessary, construct custom request headers.
#
sub geturl {

	my ($url,$request_data) = @_;
	my ($ua,$req,$res);

	$ua = new LWP::UserAgent;
	$ua->agent($agentname);

	# If there is any custom request data, then parse out
	# header fields and values, and set them in the 
	# request object.
	#
	if ($request_data) {

		my @request_line = split /\n/, $request_data;

		# Special handling for the actual GET/POST statement
		#
		my ($method,$url,$protocol) = split / +/, (shift @request_line), 3;

		$req = HTTP::Request->new (GET => $url);
		$req->method($method);
		$req->protocol($protocol);

		# Now parse out the other headers
		while (defined ($_ = shift @request_line)) {

			last unless /\S/;
			my ($key,$value) = split /:\s+/, $_, 2;

			# We need to handle the User-Agent header specifically,
			# because it's a property of the LWP::UserAgent object,
			# not the HTTP::Request object. 
			#
			if (lc($key) eq 'user-agent') {

				$ua->agent($value);
				next;

			} else {

				# This is where we set all the other headers.
				$req->header($key => $value);
			}
		}

		# We have read the last line of headers.  
		# Now slurp in lines of content, if any,
		# and insert them as the content of our request object.
		#
		my $content = join '', @request_line;
		$req->content($content) if $content;

	} else {

		# If $request_data is empty, then just create 
		# a plain-Jane request object, with the default headers.
		#
		$req = HTTP::Request->new (GET => $url);
		$req->protocol('HTTP/1.1');
	}

	# Fetch the URL!
	$res = $ua->request($req);

	# Return the request and response as objects.
	return ($req,$res);
}



#----------------------------------------------
# Daemonize:  fork, and then detatch from the local shell.
#
defined(my $pid = fork) or die "Cannot fork: $!";

if ($pid) {             # The parent exits
	print redirect($url); 
	exit 0;
}

close(STDOUT);          # The child lives on, but disconnects
                        # from the local terminal

# We opt not to close STDERR here, because we actually might
# want to see error messages at the terminal. 



#----------------------------------------------
# MAIN LOGIC:  Basically a never-ending listen loop
#
LISTEN: {

	alarm($TIMEOUT);              # (re-)set the deadman timer

	my $c = $d->accept;           # $c is a connection
	redo LISTEN unless defined $c;

	my $r = $c->get_request;      # $r is a request
	redo LISTEN unless defined $r;

	$CGI::Q = new CGI $r->content;


	#--------------------
	# Log page
	#
	if ($r->url->epath =~ /(^\/+log$|^\/+l$)/) {

		$c->send_basic_header;

		print $c 
			header,
			start_html("$Progname Transaction Logt"),
			h1("$Progname Transaction Log"),
			$menubar,
			hr,
			pre($log)
		;
		close $c;
		redo LISTEN;

	#--------------------
	# Help page
	#
	} elsif ($r->url->epath =~ /(help|info|^\/+i$|^\/+q$|^\/+h$)/) {

		$c->send_basic_header;

		print $c 
			header,
			start_html("$Progname Help Page"),
			h1("$Progname Help Page"),
			$menubar,
			hr,
			@helpinfo,
			hr,
			$menubar,
			end_html
		;
		close $c;
		redo LISTEN;
    
	#--------------------
	# Console page
	#
	} elsif ($r->url->epath =~ /(control|console|^\/+cons?$|^\/+c$)/) {

		if (param 'Shut down now') {

			# Print a nice farewll message and then exit.
			#
			$c->send_basic_header;
			print $c
				header,
				start_html("$Progname Shut Down"),
				h1("$Progname Shut Down"),
				"$Progname has been shut down.",
			;
			close $c;

			exit(0);

		} elsif (param 'Use sample') {

			$res_headers{'current'} = $res_headers{param 'sample'};
			$res_content{'current'} = $res_content{param 'sample'};

		} elsif (param 'Use previous request') {

			$request{'current'} = $request{param 'previous_request'};

		} elsif (param 'apply') {

			my ($headers,$content) =
				split( /\n\s*\n/, param('response'), 2 );

			$res_headers{'current'} = $headers . "\n";
			$res_content{'current'} = $content unless $content eq $nontext;

			my $response = "# " . $res_counter++;

			$res_headers{$response} = $res_headers{'current'};
			$res_content{$response} = $res_content{'current'};

		} elsif (param('grab') or param('custom grab')) {

			my $request_data = param('custom grab') ? param('request') : '';

			my ($req,$res) = geturl( param('remoteurl'), $request_data );

			if (param 'custom grab') {
				my $req_url            = defined $req->url ? $req->url : "";
				my $request_tag        = $req_counter++ . " - " .  $req_url ;
				$request{$request_tag} = $r->as_string;
			}

			$log .= i( escapeHTML($req->as_string) ) . $delim;
			$log .= font( 
				{color=>"green"}, escapeHTML($res->as_string)
			) . $delim;

			# Separate headers from content.  This part can probably be
			# cleaned up.
			#
			my ($headers,$content) =
				split( /\n\s*\n/, $res->as_string, 2 );

			$res_headers{'current'} = $headers . "\n";
			$res_content{'current'} = $content;

			my $req_url      = defined($req->url) ? $req->url : "";
			my $response_tag = "# " . $res_counter++ . " - " . $req_url;

			$res_headers{$response_tag} = $res_headers{'current'};
			$res_content{$response_tag} = $res_content{'current'};

			$request{'current'} = $req->as_string;
		}

		# Use the Content-Type header to figure out if the document body
		# can be displayed in browser, or if we should insert a placeholder
		# instead.  This is kludgy.  A later verion should clean up this part. 
		#
		my $document = $res_headers{'current'} . "\n" if $res_headers{'current'};

		if (
			$document =~ m/Content-Type:\s+/i 
			and 
			$document !~ m/Content-Type:\s+text/i
		) {
			$document .= $nontext;
		} else {
			$document .= $res_content{'current'} ;
		}

		$c->send_basic_header;

		print $c
			header,
			start_html("$Progname Control Panel"),
			h1("$Progname Control Panel"),
			$menubar,
			hr,
			startform("POST", $url."control"),
			p(b("Response Headers and Document Data:")),
			p, textarea(
				-name =>'response', 
				-value=>$document,
				-force=>1,
				-rows=>12,
				-cols=>75,
				-wrap=>'physical'
			),
			p, "You can ",
			submit("apply"), 
			" these edits OR use a sample response: ", 

			# Here, we dynamically create a popup menu whose items
			# are the keys of the hash %response, except for the item 'current'.
			# The keys of %response are set up as the actual sample responses
			# at the end of this script.
			#
			submit('Use sample'),
			popup_menu(
				-name    => 'sample',
				-value   => [ 
					grep { $_ ne 'current'; } 
						sort { lc($a) cmp lc($b); } keys %res_headers 
				],
				-default => 'HTML'
			),

			p,"OR you can grab response data from a remote web server, and use that as is:",
			br, textfield( -name => "remoteurl", -size => 60, -value => 'http://' ), submit("grab"),
			p(b("Request Data:")),
			p,"Here you can customize the actual request you use to grab data: ", submit("custom grab"),
			p, textarea(
				-name =>'request', 
				-value=>$request{'current'},
				-force=>1,
				-rows=>12,
				-cols=>75,
				-wrap=>'physical'
			),
			submit('Use previous request'),
			popup_menu(
				-name    => 'previous_request',
				-value   => [ 
					grep { $_ ne 'current'; } 
						sort { lc($a) cmp lc($b); } keys %request 
				],
				-default => 'HTML'
			),

			p("This daemon will die after $TIMEOUT seconds of idle time.  ",
				br,
				submit('Shut down now')
			),
			endform,
			hr,
			$menubar,

			# This is just for debugging
			h3("Your contol panel request looked like this (you can debug the debugger!):"),
			pre(font({-color=>'blue'},escapeHTML($r->as_string))),

			end_html
		;

		close $c;
		redo LISTEN;

	#--------------------
	# The actual Test Page
	#
	} else {

		# Save the request headers, so that we can use them
		# ourselves if we want to mimic the client
		#
		if (defined $r) {

			# The variable $agent will be the hash-key which identifies
			# clients which sent requests to this daemon.  It will appear 
			# in the browser in a pull-down menu, from which the user 
			# can select a previous set of request headers.
			#
			my $agent;

			if (defined($r->user_agent) and $r->user_agent ne "") {

				$agent = $r->user_agent ;
			} else {
				$agent = "Unknown";
			}

			$request{$agent} = $r->as_string;

			# Munge request, to make sure we don't inadvertantly post
			# a request back to ourselves
			#
			$request{$agent} =~ s#(GET|POST)\s+http://[^/]+(.*)\s+HTTP#$1 http://INSERT_URL$2 HTTP#;
		}

		# Send the document to the browser
		#
		print $c $res_headers{current},"\n",$res_content{current};
		close $c;

		# Log this transaction 
		#
		$log .= font(
			{color=>"blue"},
			i( escapeHTML($r->as_string) )
		) . $delim;


		# Use the Content-Type header to figure out if the document body
		# can be displayed in browser, or if we should insert a placeholder
		# instead.  This is kludgy.  A later verion should clean up this part. 
		#
		my $document = $res_headers{current} . "\n";

		if (
			$res_headers{current} =~ m/Content-Type:/i
			and 
			$res_headers{current} !~ m/Content-Type:\s+text/i
		) {
			$document .= $nontext . "\n"
		} else {
			$document .= $res_content{current} 
		}

		$log .= escapeHTML($document) . $delim;

		redo LISTEN;
	}
}


#----------------------------------------------
# The sample test pages.
# Put these into a begin block so that they will be 
# defined before the rest of the code executes. 
#
BEGIN {

$Progname = "HTTP Debugger";
$nontext  = "[non-text data]";

# The menubar, used on almost every page
#
$menubar = 
	a({href=>'/info'},"Help") .
	' - ' .
	a({href=>'/control'},"Control Panel") .
	' - ' .
	a({href=>'/log'},"Log") .
	' - ' .
	a({href=>'/'},"Test")
;


#----------------------------------
$res_headers{'HTML'} =<<EOM;
HTTP/1.1 200 OK
Date: Sat, 20 Feb 1999 16:59:12 GMT
Server: libwww-perl-daemon
Content-Type: text/html
EOM

$res_content{'HTML'} =<<EOM;
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML><HEAD><TITLE>$Progname</TITLE>
</HEAD><BODY>
<H2>Hello client! I'm an <b>HTML</b> file. </H2>
<A HREF="/c">Control Panel</A></H2>
</BODY></HTML>
EOM

#----------------------------------
$res_headers{'HTML form'} =<<EOM;
HTTP/1.1 200 OK
Date: Sat, 20 Feb 1999 16:59:12 GMT
Server: libwww-perl-daemon
Content-Type: text/html
EOM

$res_content{'HTML form'} =<<EOM;
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML><HEAD><TITLE>$Progname</TITLE>
</HEAD><BODY>
<H1>$Progname - test HTML form</H1>
$menubar
<HR>
<P>
See the <A HREF="#note">NOTE</A>. 

<H2>POST Form</H2>
<FORM action="/form.cgi" METHOD="POST">

Name:  <INPUT TYPE="text" NAME="name">
<BR>
Select Coffee: 
<SELECT NAME="coffee type">
<OPTION VALUE="regular coffee">regular coffee
<OPTION VALUE="espresso">espresso
<OPTION VALUE="latte">latte
<OPTION VALUE="quakerstate">quaker state
</SELECT>
<BR>
<INPUT TYPE=checkbox NAME=with VALUE=sugar>sugar
<INPUT TYPE=checkbox NAME=with VALUE=milk>milk
<INPUT TYPE=checkbox NAME=with VALUE=cocoa>cocoa
<INPUT TYPE=checkbox NAME=with VALUE=cinnamon>cinnamon
<BR>
<INPUT TYPE=radio NAME=size VALUE=small>small
<INPUT TYPE=radio NAME=size VALUE=medium>medium
<INPUT TYPE=radio NAME=size VALUE=large>large
<BR>
<INPUT TYPE="submit" VALUE="Submit">

</FORM>

<H2>GET Form</H2>
<FORM action="/form.cgi" METHOD="GET">

Name:  <INPUT TYPE="text" NAME="name">
<BR>
Select Coffee: 
<SELECT NAME="coffee type">
<OPTION VALUE="regular coffee">regular coffee
<OPTION VALUE="espresso">espresso
<OPTION VALUE="latte">latte
<OPTION VALUE="quakerstate">quaker state
</SELECT>
<BR>
<INPUT TYPE=checkbox NAME=with VALUE=sugar>sugar
<INPUT TYPE=checkbox NAME=with VALUE=milk>milk
<INPUT TYPE=checkbox NAME=with VALUE=cocoa>cocoa
<INPUT TYPE=checkbox NAME=with VALUE=cinnamon>cinnamon
<BR>
<INPUT TYPE=radio NAME=size VALUE=small>small
<INPUT TYPE=radio NAME=size VALUE=medium>medium
<INPUT TYPE=radio NAME=size VALUE=large>large
<BR>
<INPUT TYPE="submit" VALUE="Submit">
</FORM> 

<A NAME="note">
<P>
<B><I>NOTE:</I></B> Values here are not sticky.  This is not a comboform, it's just a plain
old-fashioned HTML form with no fancy tricks from CGI.pm.  It's just here as a
sample form so you get the idea of how this debugger lets you view HTTP transactions.
</P>
<P>
<B><I>After submitting</I></B>, go to the <A HREF="/log">log page</A> to check the results. 
Your request will appear in blue text.  
</P>
<HR>
$menubar
EOM

$res_content{'HTML form'} .= 
	"<PRE>" . ("\n") x 15 . "</PRE></BODY></HTML>\n\n";


#----------------------------------
$res_headers{'text'} =<<EOM;
HTTP/1.1 200 OK
Date: Sat, 20 Feb 1999 01:21:54 GMT
Server: libwww-perl-daemon
Content-Type: text/plain
EOM

$res_content{'text'} =<<EOM;
Hello client!  I'm a text file.
EOM

#----------------------------------
$res_headers{'302 Redirect'} =<<EOM;
HTTP/1.1 302 Found
Date: Sat, 18 Dec 1999 23:38:49 GMT
Server: Apache/1.3.9 (Unix)
Location: http://www.perl.org/
Connection: close
Content-Type: text/html
EOM

$res_content{'302 Redirect'} =<<EOM;
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML><HEAD>
<TITLE>302 Found</TITLE>
</HEAD><BODY>
<H1>Found</H1>
The document has moved <A HREF="http://www.perl.org/">here</A>.<P>
<HR>
</BODY></HTML>
EOM

#----------------------------------
$res_headers{'401 Unauthorized'} =<<EOM;
HTTP/1.1 401 (Unauthorized) Authorization Required
Connection: close
Date: Sat, 18 Dec 1999 21:17:10 GMT
Server: Apache/1.3.6 Ben-SSL/1.34 (Unix) mod_perl/1.19_01-dev
WWW-Authenticate: Basic realm="PAUSE"
Content-Type: text/html
Client-Date: Sat, 18 Dec 1999 21:14:58 GMT
Client-Peer: 212.40.160.59:80
Title: 401 Authorization Required
EOM

$res_content{'401 Unauthorized'} =<<EOM;
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<HTML><HEAD>
<TITLE>401 Authorization Required</TITLE>
</HEAD><BODY>
<H1>Authorization Required</H1>
This server could not verify that you
are authorized to access the document
requested.  Either you supplied the wrong
credentials (e.g., bad password), or your
browser doesn't understand how to supply
the credentials required.<P>
</BODY></HTML>
EOM

#----------------------------------
$res_headers{'403 Forbidden'} =<<EOM;
HTTP/1.1 403 Forbidden
Connection: close
Date: Sat, 18 Dec 1999 19:59:25 GMT
Server: Apache/1.2.4 mod_perl/1.07
Content-Type: text/html
Client-Date: Sat, 18 Dec 1999 20:49:39 GMT
Client-Peer: 192.168.17.1:80
Title: 403 Forbidden
EOM

$res_content{'403 Forbidden'} =<<EOM;
<HTML><HEAD>
<TITLE>403 Forbidden</TITLE>
</HEAD><BODY>
<H1>Forbidden</H1>
You don't have permission to access /offlimits
on this server.<P>
</BODY></HTML>
EOM


#----------------------------------
$res_headers{'404 Not Found'} =<<EOM;
HTTP/1.0 404 Not Found
Date: Sat, 20 Feb 1999 02:51:02 GMT
Server: NCSA/1.5
Content-Type: text/html
Client-Date: Sat, 20 Nov 1999 02:49:07 GMT
Client-Peer: 207.29.195.3:80
Title: 404 Not Found
EOM

$res_content{'404 Not Found'} =<<EOM;
<HEAD><TITLE>404 Not Found</TITLE></HEAD>
<BODY><H1>404 Not Found</H1>
The requested URL was not found on this server.
</BODY>
EOM

#----------------------------------
$res_headers{'500 Server Error'} =<<EOM;
HTTP/1.0 500 (Internal Server Error) Server Error
Date: Sat, 20 Feb 1999 02:44:04 GMT
Server: NCSA/1.5
Content-Type: text/html
Client-Date: Sat, 20 Nov 1999 02:42:08 GMT
Client-Peer: 207.29.195.3:80
Title: 500 Server Error
EOM

$res_content{'500 Server Error'} =<<EOM;
<HEAD><TITLE>500 Server Error</TITLE></HEAD>
<BODY><H1>500 Server Error</H1>
The server encountered an internal error or
misconfiguration and was unable to complete 
your request.<P>
Please contact the server administrator, webmaster\@op.net and 
inform them of the time the error occurred, and anything you might 
have done that may have caused the error.<P>
<b>Error:</b> HTTPd: malformed header from script /cgi-bin/myscript.cgi
</BODY>
EOM


#----------------------------------
my $gifdata =<<EOM;
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EOM


# We pack this data into a GIF image, and use it below
#
$gifdata =~ s/\n//gm;
my $gif       = pack "H*",$gifdata;
my $giflength = length $gif;


$res_content{'GIF'} = $gif;
$res_headers{'GIF'} =<<EOM;
HTTP/1.1 200 OK
Connection: close
Date: Sat, 18 Dec 1999 16:47:56 GMT
Accept-Ranges: bytes
Server: Apache/1.2.4 mod_perl/1.07
Content-Length: $giflength
Content-Type: image/gif
ETag: "142bc-14c4-385bba51"
Last-Modified: Sat, 18 Dec 1999 16:46:09 GMT
Client-Date: Sat, 18 Dec 1999 17:38:08 GMT
Client-Peer: 192.168.17.1:80
EOM

}


#----------------------------------------------
__END__

<H2>What is this thing?</H2>

<p>
This is a tool to help you debug HTTP transactions.  It uses both 
the HTTP server and HTTP client functionalities of the LWP bundle.  
It helps you easily mimic and tweak transactions between servers and clients.  
You operate this program using a Web browser. 
</p>

<p>
When you launch this program from the command line, it becomes 
a tiny HTTP daemon.  For example, if you launch this program with
the parameter "-p 8080", then it will become a Web server 
on port 8080.  You can then access it using a browser at the URL 
"http://host.domain.com:8080/c".  The page that you will
see is a control panel for the program.  
</p>

<p>
With any other URL besides "/c" (and a few other paths),
this little server will only print out a brief test page (i.e.,
test headers and a test document). From the control panel, 
you can specifically adjust the test headers and the test document 
that the server (this program) sends to the client (something else), 
and then watch how the client responds.  
</p>

<p>
All transactions are logged, and you can view these 
transaction logs right from the browser, by using
the path "/l" or "/log". 
</p>

<p>
You can use the debugger's HTTP client functionality to interact with 
a remote web server.  From the control panel, you can specify a URL,
and the debugger (as HTTP client) will that request to a remote
Web server and save the response headers and document. 
If you want, you can manually adjust the header data and
request lines that the HTTP client uses during this transaction.
</p>

<p>
After fetching a document like this, the debugger's server functionality 
can immediately use this information to mimic that remote server.  
In this way, you can very easily simulate the interactions between 
a remote server and a remote client, by just making your little server 
behave exactly like the remote server.
</p>
 
<p>
You can very carefully tweak the headers and document data 
that you are sending and receiving.  This can be useful for 
locating otherwise obscure errors. 
</p>

<p>
The debugger has a built-in timeout, which by default is 180 seconds.
This helps prevent you from launching the HTTP daemon and then
forgetting that it's running, which could be a security issue. 
When you launch the program from the command line, use the -t option
to specify a timeout (in seconds).  The program will exit
after that number of seconds of idle time. 
</p>


<H2>The Log page</H2>

<p>
The debugger has a log page, where it records the data transferred
(both headers and data) during HTTP transactions. On the log page, 
this is the color scheme:
</p>

<p align=center>
<tt>
	<font color=blue><i>Remote client</i></font> 
	&lt;-&gt;
	Local server 
	<br>
	<i>Local client</i> 
	&lt;-&gt;
	<font color=green>Remote server</font> 
</tt>
</p>
<p>
Headers and data are all the same color.  They are separated
by two newlines, of course. 
</p>

<p>
The debugger does not log transactions made when it
serves up the control panel, the log page, nor this help page.
</p>

<H2>Special URLs</H2>

Below is a list of all the URLs that are "special" for this 
Web server:

<PRE>
Control panel: /c  /con /cons /console /control
Log page:      /l  /log
Help page:     /i  /info /h /help /q
</PRE>

Any other URLs will result in the sending of the test page
as a response. 

<H2>Do I really need this thing?</H2>

<p>
Maybe not.  You can do practically all of these things
from the command line using netcat.  But it's a lot
trickier that way, especially if you are not a die-hard
command-line jockey.  This interface is certainly faster,
and it keeps a nice handy log of all transactions. 
Plus it has pretty colors.  :-)
</p>

<H2>Complaints, suggestions, improvements</H2>

<p>
Please send mail to the author at 
<a href=mailto:jpnolan@sonic.net>jpnolan@sonic.net</a>. 
</p>