AJAX Tutorial - Felix John COLIBRI.

• abstract : writing an AJAX web application. How AJAX works, using a JavaScript DOM parser, the Indy Web Server, requesting .XML data packets - Integrated development project
  
• key words : AJAX - XMLHttpRequest - XML DOM - DOM parser - Indy tIdHttpServer - tWebBrowser
  
• software used : Windows XP Home, Delphi 6, Indy 8.5, Internet Explorer 6.0
  
• hardware used : Pentium 2.800Mhz, 512 M memory, 140 G hard disc
  
• scope : Delphi 1 to 2006, Turbo Delphi for Windows, Delphi 2007, RAS Studio 2007
  
• level : Delphi developer
  
• plan :
  
  • Why use AJAX technology
    
  • Simple AJAX implementation
    
  • AJAX in perspective
    
  • Download the Sources
    

1 - Why use AJAX technology

For pages with heavy overhead and many data refresh, it becomes more efficient to load the background page and the multiple data requests separately. And this can be done using AJAX.

2 - Simple AJAX implementation

2.1 - How AJAX works

When a page contains some data which can change, like a DataGrid with paging, whenever the user wants the next page of data, the whole page is built by the Server and reloaded (that is analyzed, displayed) by the Browser:

So even if some pieces (images) are cached by the Browser, the Browser still has to analyze and layout the page, even if only a couple of strings have changed in the display

Here is an illustration of the standard way of operating:

• the user requests some page with the first rows of some data table

• when the user request the next data pieces, the new requests brings the whole page back, with the new data:

To do so, AJAX relies basically on 2 JavaScript techniques

• the ability to request only data from the Server, which is done using an XMLHTTPRequest call
  
• grafting some parts in page analyzed and displayed by the Browser, using innerHTML or similar technique
  

• the first request loads the base page:

• when the second and next data pieces are requested (paging in a DataGrid, for instance), only the data payload is transferred from the Server:

• for the first page, we could use the standard "page+data" transfer. In our illustration, we assumed that even for the first page the data was loaded separately. But of course, this is not mandatory.
  

2.2 - Our AJAX example

	the user requests our ARTICLE_LIST page
	our server returns the page with the first 4 article rows
	the user clicks the "next_article" link
	the next 4 article rows are fetched and displayed

2.3 - JavaScript Crash Course

2.3.1 - Javascript: a Client Side Interpreter

Enters JavaScript: a client side interpreter which can execute scripts which are sent from the Server to the Client along with the main .HTML. Those scripts are able to execute code statements, among which

• do some event handling for mouse events
  
• call some routine when the user click on an hyperlink.
  

2.3.2 - OnClick

For instance, to change the color of a .HTM page in red when the user click the "red" link:

• we identify the area which should be modified with a unique ID
  
• we create a SCRIPT tag containing a routine which finds the area to paint, and changes its color style attribute
  
• we create a link which, when clicked, will call the JavaScript routine
  

and

• our BODY tag contains an ID attribute with our "my_body" unique identifier
  
• the SCRIPT tag contains the color changing routine
  
• the hyperlink "red" is defined by the usual A anchor tag, which contains a call to our coloring routine
  

To run this example, you may

	copy the text to the ClipBoard
	start NotePad, paste the code
	"save as" with an .HTML extension
	double click on the disc file, and let Internet Explorer display the result

CAUTION

• the .HTML tag name (like BODY) and attribute name (like HREF) are case insensitive. It seems that the specification requires uppercase, but nobody follows this anyway, so most of the browser have learned to live with this
  
• the JavaScript language on the other hand IS CASE SENSITIVE and writing BackgroundColor usually will not work. In addition most of the names follow the Java convention: first lowercase and additional names with a first capital. Like getElementById
  

2.3.3 - Unique tag ID s

• we simply include an ID attribute with a unique value
  
• we access this value using

  my_element = Document.getElementById(my_id_value);

  
  

• the full .HTML page is the Document JavaScript object
  
• this object has attributes and methods, and the getElementById is a search function returning the object with this ID. So the result is another JavaScript object
  
• the returned object in turn has attributes and methods. In our example, we used the style attribute
  
• we could have used other attributes
  

with the following snapshot :

2.3.4 - Replace a content: innerHTML

In the following example, clicking "text" will add "AHA" and clicking "table" will add a table:

If we clic "table", "text", "text", we will get:

Please note

• this is, in fact, the easiest way to build a debugging log on a Page: just add a DIV tag and append text using innterHTML.
  
• innerHTML seems to be frowned at by some JavaScript developers, and the argument seems to be "making a mistake in the replacement could break the page". Well, if writing bugs would have deterred us from programming ...
  

2.4 - Reading .XML from the Server

• we must create an xmlhttprequest object which can be native or an ActiveX component

  var my_c_xml_http_request; if (window.xmlhttprequest)   {     // -- use Native XMLHttpRequest     my_c_xml_http_request = new xmlhttprequest();   } else   if (window.activexobject)     {       // -- use IE/Windows ActiveX       my_c_xml_http_request = new activexobject("Microsoft.XMLHTTP");     } if (my_c_xml_http_request == null)   alert("does not support xml_http_request");

• we use this object to call open and send

  // -- prepare the GET my_c_xml_http_request.open("GET", '/my_data.xml', true); // -- request the file by sending the GET my_c_xml_http_request.send(null);

  This works, but after the send call, the data is not transferred on the spot: there is a call to the Server, which might have some delay, or the line could be slow. Therefore, to synchronize the reception, xmlhttprequest has a callback, called onreadystatechange in which we can test the xmlhttprequest.readyState: a value of 4 means that the .XML has been received.

  Therefore, the retrieval should use some code like:

  function on_readystate_change()     // -- called once the .XML has been received   {     if (my_c_xml_http_request.readystate == 4)       {         // -- the download is finished         if (my_c_xml_http_request.status != 200)           alert('error loading HML file.  Status: '             + my_c_xml_http_request.status + ' '             + my_c_xml_http_request.statustext);         // -- do some handling on         // -- my_c_xml_http_request.responseText;       }     else       {         // -- tell the user that the transfer is         // -- proceeding       }   } // on_readystate_change // -- set the state change handler my_c_xml_http_request.onreadystatechange = on_readystate_change; // -- prepare the GET my_c_xml_http_request.open("GET", '/my_data.xml', true); // -- request the file by sending the GET my_c_xml_http_request.send(null);

  
  

Note that

• in the previous example, we placed the SCRIPT tag within the HEAD tag (instead of in the BODY section). Both are accepted, and we can even use several SCRIPT sections, both in HEAD or BODY. And when our trials are finished, we could also externalize the whole script in an external .JS file

• our Page contains a TEXTAREA memo for displaying the text of the received .XML. This is where the innerHTML could disrupt the .HTML Page: the .XML contains tags, which usually have nothing to do whith bona fide .HTML tags

• but what exactly is is the .XML ? That depends on what the Server answers when it gets the .XML request. And this is our next step.
  

2.5 - Building an .HTTP Server

2.5.1 - The .XML request

And the Server should send back something like:

2.5.2 - The .HTTP Server

Since the purpose of this article is not .HTTP Server implementation, we will use the Indy tIdHTTPServer which comes with Delphi.

This Server is quite easy to use:

• toggle Active to True
  
• create the CommandGet event and build the response
  

Our Server will be called two times:

• when the user requests the INDEX.HTML home page
  
• when the user clicks the link to get the ARTICLE_LIST.XML
  

Depending on the Document, we either load the INDEX.HTML, or build the .XML string

Here are all the Indy components and properties we will use:

Here is our complete Server

	select "File | New | Application" and save it as AJAX_TUTORIAL
	from the "Indy Servers" tab of the Tools Palette, select the tIdHTTPServer: and drop it on the tForm
	add a tButton an toggle IdHTTPServer.Active to True, which will start the Server listening
	create the CommandGet event, and write the code which will build the response to the possible requests (the initial .HTML and the .XML article list): procedure TForm1.IdHTTPServer1CommandGet(AThread: TIdPeerThread;     RequestInfo: TIdHTTPRequestInfo; ResponseInfo: TIdHTTPResponseInfo);   function f_build_static_response(p_requested_document: String): String;     var l_file_name, l_new_file_name: String;         l_index: Integer;     begin       // -- convert all '/' to '\'       l_file_name:= f_replace_character(p_requested_document, '/', '\');       // -- locate requested file       l_file_name:= g_path+ l_file_name;       if AnsiLastChar(l_file_name)^= '\'         then // -- folder - reroute to default document              l_new_file_name:= l_file_name+ g_file_name         else // -- a file request: use this file name              l_new_file_name:= l_file_name;         if FileExists(l_new_file_name)           then Result:= f_load_string(l_new_file_name)           else begin               // -- some error               display_bug_stop('not_found '+ l_new_file_name);             end;     end; // f_build_static_response   function f_xml_response(p_request_command: String;       p_c_request_params: tStrings): String;     var l_row_index: Integer;         l_start_index, l_row_count: Integer;     begin       with tStringList.Create do       begin         Add('<xml>');         Add('  <updated>01 October 2007</updated>');         Add('  <articles>');         Add('    <article id="063" title="Ajax Tutorial"'             + ' date="1/oct/2007" />');         Add('    <article id="062" title="BlackfishSql"'             + ' date="24/sep/2007" />');         Add('    <article id="061" title="Dbx4 Programming"'             + ' date="19/sep/2007" />');         Add('  </articles>');         Add('</xml>');         Result:= Text;         Free;       end; // with tStringList.Create     end; // f_xml_response   var l_requested_document: String;       l_extension: String;   begin // IdHTTPServer1CommandGet     l_requested_document:= RequestInfo.Document;     // -- either load a static page, or build a dynamic .XML response     if l_requested_document = '/article_list.xml'       then begin           ResponseInfo.ContentType:= 'text/xml';           ResponseInfo.ContentText:=               f_xml_response(l_requested_document, RequestInfo.Params);         end       else begin           // -- build 'Content-Type header"           l_extension:= ExtractFileExt(l_requested_document);           display('Ext '+ l_extension);           if l_extension= '.css'             then ResponseInfo.ContentType:= 'text/css'             else               if l_extension= '.js'                 then ResponseInfo.ContentType:= 'text/javascript'                 else ResponseInfo.ContentType:= 'text/html';           ResponseInfo.ContentText:=               f_build_static_response(l_requested_document);          end;   end; // IdHTTPServer1CommandGet
	compile, run and click "active" to start the Server
	start Internet Explorer and request     http://127.0.0.1/index.html
	the page with the "article_list" link is displayed
	click this link
	the .XML file is displayed in the TEXTAREA:

Note that

• we built the .XML entirely from code. This could have been loaded from some text file, or, better, from a database
  
• you will notice that we also would have served .CSS and .JS files, if our INDEX.HTML had referenced such files
  

2.6 - Analyzing the response .XML

To be able to handle the .XML tree :

• the .XML response MUST have a "Content-Type : text/xml" value
  
• we must drill down into the .XML using the .DOM (Document Object Model) INTERFACE available in JavaScript
  

2.6.1 - Extracting the .XML values

In our case, the .XML was:

and we would like to display something perhaps like this :

To extract the .XML values

• we get an .XML document object

  my_c_xml_node = my_c_xml_http_request.responseXml;

• to navigate this tree, we can use
  
  • my_c_node.firstChild to get one level down
    
  • my_c_node.nextSibling to get the neighbouring node
    
  • my_c_node.getElementsByTagName('my_tag') to get a list of nodes with some tag name. This list can be explored using length and indexing into the list
    

• my_c_node.nodeType 1 which is a so called "element", which can have attributes

  <article id="062" title="BlackfishSql" date="24/sep/2007" />

  and:

  • "article" is a type 1 "element", with attributes "id", "title" and "date"
    
    
• my_c_node.nodeType 3, a "text" node, with a my_c_node.Data text content

  <updated>01 October 2007</updated>

  and:

  • "updated" is an "element" (type 1)
    
  • ITS CHILD is the "text" (type 3) with content "01 October 2007"
    

where do_display() is the JavaScript version of our traditional indented log. This log JavaScript is in the source .ZIP which comes with this article. Here is the result with our .XML example (as copied from the TEXTAREA log memo):

Using this knowledge, we can now fill a TEXTAREA with the .XML values:

and getting the page in Internet Explorer:

2.6.2 - Sending Parameters to the Server

In order to be able to paginate thru the data, our request has to send, as parameters, the start value and the count, and to manage the current starting point at the Client.

Using JavaScript

• we can save in a variable the current starting row
  
• when we request the next page, we have to send the next starting row and the requested count as parameters in the URL
  
• the Server on the other side will extract those parameters, and build an .XML response taylored to those parameters.
  

• ? and the key=value for the first parameter
  
• & and the key=value for the next parameter
  

In order to implement this

• for the .HTML page
  
  • our JavaScript declares 2 global variables, g_start_row, and g_row_count
    
  • our main "article_list" link will call a function which fetches the first row packet
    
  • we added a "Next" link on the .HTML page which increments the
    
  • this link increments the g_start_row, and grabs the next row packet
    
• on the Server
  
  • we check for the presence of parameters. If this is the case, we extract the parameter values using RequestInfo.Params.Values:

    var my_start_row, my_row_count: Integer;   with RequestInfo.Params do   begin     my_start_row:= StrToInt(Values['start_row']);     my_row_count:= StrToInt(Values['row_count']);   end; // with RequestInfo.Params

  • we load from an .TXT file the article list in a tStringList, and use this list to add the requested articles to the response
    

• in the .HTML, we implement paging:

  <HTML>   <HEAD>     <SCRIPT>       function load_xml(p_xml_file_name)         {           var l_c_xml_http_request;             function create_xml_http_request()             {               if (window.XMLHttpRequest)                 {                   l_c_xml_http_request = new XMLHttpRequest();                 }               else                 if (window.ActiveXObject)                   {                     l_c_xml_http_request = new ActiveXObject("Microsoft.XMLHTTP");                   }               if (l_c_xml_http_request == null)                 alert("does not support xml_http_request");             } // create_xml_http_request             function get_and_parse_xml()             {               // -- set the handler               l_c_xml_http_request.onreadystatechange = on_readystate_change;               // -- request the file by sending a GET               l_c_xml_http_request.open("GET", p_xml_file_name, true);                 // -- acknowledge end               l_c_xml_http_request.send(null);             } // get_and_parse_xml             function on_readystate_change()               // -- called once the .XML has been received             {               if (l_c_xml_http_request.readyState == 4)                 {                   if (l_c_xml_http_request.status != 200)                     alert('error loading HML file. Status: '                       + l_c_xml_http_request.status + ' '                       + l_c_xml_http_request.statusText);                     analyze_xml(l_c_xml_http_request.responseXml);                 }               else                 {                   // alert('error readystate '+ l_c_xml_http_request.readyState);                 }             } // on_readystate_change             function analyze_xml(p_c_xml_root_node)             {               var l_result_display= 'last updated : \n ';                 l_c_updated_list = p_c_xml_root_node.getElementsByTagName('updated');               l_c_updated_node= l_c_updated_list[0];               l_result_display += l_c_updated_node.firstChild.data + '\n ';                 l_c_article_list = p_c_xml_root_node.getElementsByTagName('article');               l_article_count= l_c_article_list.length;               for (var l_index= 0; l_index< l_article_count; l_index ++ )                 {                   l_c_article_node= l_c_article_list[l_index];                     l_article = '';                   for (var l_attribute= 0;                         l_attribute< l_c_article_node.attributes.length;                         l_attribute ++)                     l_article += l_c_article_node.attributes[l_attribute].nodeValue+ ' ';                     l_result_display += l_article+ '\n';                 };                 l_memo_ref= window.document.display_form.display_memo;               l_memo_ref.value = l_result_display;             } // analyze_xml             create_xml_http_request();           get_and_parse_xml();         } // load_xml         var g_start_row= 0;       var g_row_count= 3;       var g_xml_page_name;         function get_next_article_page(p_xml_page_name)         {           g_xml_page_name= p_xml_page_name;             l_request= p_xml_page_name               + '?start_row='+ g_start_row               + '&row_count='+ g_row_count ;             load_xml(l_request);         } // get_next_article_page          function get_next_page()          {           g_start_row += g_row_count;           get_next_article_page(g_xml_page_name);          } // get_next_page     </SCRIPT>   </HEAD>   <BODY>     <DIV>       <A href="#" onClick="get_next_article_page('/article_list.xml');">          article_list</A><BR>     </DIV>     <DIV>       <FORM name="display_form">         <TEXTAREA name="display_memo" rows=10 cols=10></TEXTAREA>       </FORM>     </DIV>     <DIV>         <A href="#" onClick="get_next_page();">next</A><BR>     </DIV>   </BODY> </HTML>

• in the Indy Server:

  procedure TForm1.IdHTTPServer1CommandGet(AThread: TIdPeerThread;     RequestInfo: TIdHTTPRequestInfo; ResponseInfo: TIdHTTPResponseInfo);   function f_build_static_response(p_requested_document: String): String;     begin       // -- ...ooo... as before     end; // f_build_static_response   function f_xml_response(p_request_command: String;       p_c_request_params: tStrings): String;     procedure build_response;       begin         with tStringList.Create do         begin           Add('<xml>');           Add('  <updated>01 October 2007</updated>');           Add('  <articles>');           Add('    <article id="063" title="Ajax Tutorial" date="1/oct/2007" />');           Add('    <article id="062" title="BlackfishSql" date="24/sep/2007" />');           Add('    <article id="061" title="Dbx4 Programming" date="19/sep/2007" />');           Add('  </articles>');           Add('</xml>');           Result:= Text;         end; // with tStringList.Create       end; // build_response     procedure build_parametrized_response;       var l_start_row, l_row_count: Integer;           l_c_article_parameter_list: tStringList;           l_row_index: Integer;       begin         with RequestInfo.Params do         begin           l_start_row:= StrToInt(Values['start_row']);           l_row_count:= StrToInt(Values['row_count']);         end; // with RequestInfo.Params         l_c_article_parameter_list:= tStringList.Create;         l_c_article_parameter_list.LoadFromFile(f_exe_path+ k_article_parameter_file_name);         with tStringList.Create do         begin           Add('<xml>');           Add('  <updated>01 October 2007</updated>');           Add('  <articles>');           for l_row_index:= l_start_row to l_start_row+ l_row_count- 1 do             Add('    <article '+ l_c_article_parameter_list[l_row_index]+ ' />');           Add('  </articles>');           Add('</xml>');           Result:= Text;           Free;         end; // with tStringList.Create         l_c_article_parameter_list.Free;       end; // build_parametrized_response     begin // f_xml_response       if RequestInfo.Params.Count> 0         then build_parametrized_response         else build_response;     end; // f_xml_response   var l_requested_document: String;       l_extension: String;   begin // IdHTTPServer1CommandGet     // -- requested document     l_requested_document:= RequestInfo.Document;      // -- build the content: either initial static page,      // --   or dynamic .XML data      if f_start_is_equal_to(l_requested_document, '/article_list.xml')        then begin            // -- must be present or will not see .XML            ResponseInfo.ContentType:= 'text/xml';            ResponseInfo.ContentText:=                f_xml_response(l_requested_document, RequestInfo.Params);          end        else begin            // -- build 'Content-Type header"            l_extension:= ExtractFileExt(l_requested_document);            if l_extension= '.css'              then ResponseInfo.ContentType:= 'text/css'              else                if l_extension= '.js'                  then ResponseInfo.ContentType:= 'text/javascript'                  else ResponseInfo.ContentType:= 'text/html';            ResponseInfo.ContentText:=               f_build_static_response(l_requested_document);          end;     end;   end; // IdHTTPServer1CommandGet

• the snapshot of clicking "article_list" and "next":

  
  

• we only adde "next". Obviously "previous", or "first", "last" or entering the row count in a input box could be easily added
  
• we also could have built (statically or using JavaScript) a nice grid (using <TABLE>) and even with a nice row header
  

2.6.3 - .XML selective data extraction

First, we create a call back mechanism:

• the XML DOM analyzer built a tree in memory
  
• we walk this tree in the usual to-down, left-right way
  
• if the XML tag name belongs to some predefined names, we call the corresponding handling event
  

and our main .XML load and analysis script becomes:

Please note that

• in this example we displayed all the attributes, but we could have filtered some fields using tests on the attribute value, or the my_c_node.getAttribute(my_key) function

  Here is a snapshot with all the articles, and indented after each row, the "date" and "title" extracted with

  l_article += '\n'    + ' ['+ p_c_article_node.getattribute('date')+ '] '    + p_c_article_node.getattribute('title');

  with the following result:

  

• we only added one callback. But we could have added other callbacks, like a callback on the "updated" tag
  

2.6.4 - JavaScript and DOM objects

2.7 - Javascript Development Tool

2.7.1 - Debugging JavaScript

This was not so easy, because JavaScript is quite brittle, as seen by a Pascal developer. Here are just a few among the many bugs we encountered:

• from JavaScript:
  
  • omission of VAR in FOR index
    
  • wrong casing, like NodeValue instead of nodeValue
    
  • many missing string ending quotes
    
  • the mysterious ending ";" rule
    
  • some difficulties in selecting between Value, nodeValue or Data
    
  • the usual C mistakes of a hard dyed Pascal programmer : "=" instead of "=="
    
• a fundamental logical bug: we wanted to initialize the display and present it before and after calling get_and_parse_xml(). This does not work, since the loading is an ASYNCHRONOUS call: the control returns instantaneously after the call, and any processing performed after the call is not guaranteed to work on the received answer. The event on_readystate_change was precisely created to cope with this decoupling: when the state is 4, we know that the response has been received
  
• on the Server side, we also had mistakes, like a mission </articles> tag for instance
  

2.7.2 - The JavaScript Log

Here is the minimal version of this logging tool:

And here is a snapshot of the log in tWebBrowser:

If you do not want to use the logging facility, simply write an empty do_display() routine, or, more radical, remove all calls to do_display()

2.7.3 - An integrated environment

• Delphi to create the Web Server using the Indy .HTTP Server
  
• NotePad to write the .HTML page and the JavaScript scripts
  
• Internet Explorer to get the initial page, and paginate thru the .XML data, which is the fundamental purpose of AJAX
  

• first added the possibility to edit the .HTML page from within our application. We simply load the .HTML in a tMemo, and save the resulting text into the .HTML file. And we have thrown in an "history" copy before overwriting the .HTML with its new version

• to alleviate the burden of starting the IE Browser, we first added a button which copied the correct URL in the Clipboard. It worked. However, sadly enough, mistakes still were not reported by IE. The page stayed blank with no message whatsoever.

  So we integrated a tWebBrowser in the application, which allows to display the .HTML page, and to click on the links. It was some surprise to find out that the embedded tWebBrowser did flag the mistakes, being so kind as to sometimes give us a hint like "object xxx unknown", "this object does not handle method mm" or "zzz requires an object". There MUST be a way to get the same messages from the standalone Internet Explorer, but since our embedded tWebBrowser worked, we did not investigate it any more.

• here is a snapshot of the .ZIP version with the last example:

  
  

• a DirectoryListBox and FileListBox, allowing us to load different .HTML files
  
• the chosen .HTML is loaded in a Memo, which has elementary search capability. Of course the text can be saved back on disk with the same name or another name
  
• when we are satisfied with the .HTML, we can start the WebBrowser (start the first time, refresh after this). We even can start this by using F9 from the tMemo !
  

3 - AJAX in perspective

3.1 - Internet Express

We have long ignored this, since we did not want to touch JavaScript, even with a ten-foot pole. When we tried to do some web accounting package, we looked more deeply at it, but did not fully grasp the intent and benefits of this framework. Well, is is AJAX long before this term was coined.

3.2 - AJAX Libraries

We used here some kind of "homegrown AJAX". But for industrial use, we would search for some libraries, which make the exchange between the Browser and the Server more easy.

There are many such libraries, even in source code, that you can find using Google. With Delphi, we already have two libraries:

• for Win32, Intraweb (VCL for the Web as is is now called) offers such a library
  
• for .Net, the new RAD Studio 2007 allows us to use the Asp.Net 2.0 AJAX library (ATLAS)
  

4 - Download the Sources

• ajax_tutorial.zip: the integrated FileListBox loader, .Html memo editor, Http Server, and WebBrowser (32 K)
  
• ajax_html_demos.zip: the .HTML used in this AJAX tutorial (3 K):
  
  • javascript_log.html : our indented JavaScript log
    
  • js_01_color_red.html : OnClick event
    
  • js_02_color_element.html : referencing a tag ID
    
  • js_03_inner_html.html : replacing the content of a tag
    
  • log_10_xml_request.html : fetching some .XML content from the Server
    
  • log_11_analyze_xml.html : extracting the .XML text and attribute values
    
  • log_14_send_parameters_paginate.html : sending parameters to the Server to paginate thru the data
    
  • log_15_extraction_callback.html : using callbacks to automate tag extraction
    

• the main program (.DPR, .DOF, .RES), the main form (.PAS, .DFM), and any other auxiliary form
  
• any .TXT for parameters, samples, test data
  
• all units (.PAS) for units
  

• are self-contained: you will not need any other product (unless expressly mentioned).
  
• for Delphi 6 projects, can be used from any folder (the pathes are RELATIVE)
  
• will not modify your PC in any way beyond the path where you placed the .ZIP (no registry changes, no path creation etc).
  

• create or select any folder of your choice
  
• unzip the downloaded file
  
• using Delphi, compile and execute
  

The Pascal code uses the Alsacian notation, which prefixes identifier by program area: K_onstant, T_ype, G_lobal, L_ocal, P_arametre, F_unction, C_lass etc. This notation is presented in the Alsacian Notation paper.

As usual:

• please tell us at fcolibri@felix-colibri.com if you found some errors, mistakes, bugs, broken links or had some problem downloading the file. Resulting corrections will be helpful for other readers
  
• we welcome any comment, criticism, enhancement, other sources or reference suggestion. Just send an e-mail to fcolibri@felix-colibri.com.
  
• or more simply, enter your (anonymous or with your e-mail if you want an answer) comments below and clic the "send" button

  Name :
  E-mail :
  Comments * :

• and if you liked this article, talk about this site to your fellow developpers, add a link to your links page ou mention our articles in your blog or newsgroup posts when relevant. That's the way we operate: the more traffic and Google references we get, the more articles we will write.
  

5 - See Also

• The TCP/IP Sniffer which was used to monitor the packet exchanges between the Http Server and the (standalone) Internet Explorer. Indy does have properties to get the full Headers, but this is not as complete as using a bona fide TCP/IP sniffer
  
• the papers used our last published papers as the database example. And in this paper list is an article about programming the brand new BlackfichSql standalond database of RAD Studio 2007. Well it turns out that we could have placed the article list in a database managed by Blackfish Sql
  
• we also organize frequent Web Programming trainings (Socket programming, Asp.Net 1.0 and Asp.Net 2.0 with Delphi, Intraweb programming)
  

6 - The author