SQUEAK CROQUET TUTORIAL

CROQUET MEETS JAVA OR .NET

The next step in our "Bookstore project" would be to create the logic for the buyer to send his data to the server of the bookstore.

But, before to do this, we need to remember how a modern network application works today.

There are the concept of 3 tiers, like you can say in the figure.

We are presenting, in the figure, 2 professional sceneries: the first uses Java and the other the .NET architecture.

We will work, at this course,in a very simplified way (the 3th scenery) using Squeak-Croquet at the first tier - using its Smaltalk language. In the 2nd tier we will use ASP.Net with JavaScript, a very usual choice.

To do our exercices, if your server is not Windows (having the .NET framework and ACCESS database) it' s easy to find a cheap web-hoster having this configuration. Some are free, but can have some restrictions and bad performance. By ethics reasons I can't recomend any service provider. Sorry.

At our first exercice about 3 tiers applications using Squeak-Croquet we will create a project where: the user types a word in a TextField, clicks a Button and the string goes to the server and returns like an echo to other TextField.

We will have this objects:

The script glued to the object Click (a rectangle having a text - event: MouseDown) will be:

| page parsedPage thebody clean |
Msg2  show.
page:=HTTPSocket httpGet:'http://www.dmu.com/croquet/echo.aspx?thename=', Shout1 getCharacters.
parsedPage := HtmlParser parse: page. 
thebody := parsedPage body.
clean := thebody   contents at:1 .  
clean := clean  asString .
clean := clean copyReplaceAll: '[' with:''. 
clean := clean copyReplaceAll: ']' with:''. 
Echo1 setCharacters: clean.

CODE COMMENTS

1 - There are a hiden message: "Message sended.Wait..." - look the figure in the botton of this page - that will appear when the user clicks the rectangle.
2 - The function httpGet of the Class HTTPSocket calls the ASPX program (echo.aspx) in the server, sending the variable: thename having the content of the TextField Shout

3 - This ASPX program - we will see it soon - takes this value of the variable and add it after a string: "echo for =" and send it back to the machine of the user, but adding some aditional things that need to be cleaned. This lines do it:

                    thebody := parsedPage body.
                    clean := thebody   contents at:1 .  
                    clean := clean  asString .
                    clean := clean copyReplaceAll: '[' with:''. 
                    clean := clean copyReplaceAll: ']' with:''.

This code will be the same for any answer of the server.

4 - The last line of the code sets the answer in the Echo TextField.

VERY VERY IMPORTANT: The objects change their names during the codification when something changes on them, adding new numbers of versions. This is not usual in other languages...IF YOU ARE HAVING PROBLEMS, VERIFY ALL THE NAMES, AND THEIR DESIGNATIONS IN THE CODE!

The ASPX program is coded in JavaScript and is uploaded to that path in the server:

<script language="JavaScript" runat="server">
function Page_Load(sender:Object, e:EventArgs):void{
 var thename=this.Request.Params["thename"];
 Response.Write("echo for = " + thename); 
}
</script>

CODE COMMENTS

1 - The function Page_Load runs when the program is called by the user.
2 - The value of the element of this.Request.Params is the value of the variable sended.
3 - The parameter of Response.Write will be the message returned to the user.
4 - In JavaScript we do concatenation using the "plus signal", not comma.

Glued to the TextField Shout we have a simple script triggered when the user "MouseStillDown" - clicks and remains with the mouse-button down - this field. It will do this trying to type a new message.

Msg2  hide

You can test this project!

Its address is: http://www.dmu.com/Tealand/echo1.006.pr

And re-read the lesson about how to create a 3D window for a project. Use for "extent": 1050 x 1050.

Look some images of the project working:

WARNING. If you don't have a powerfull computer and a fast communication line it's possible that you will not have a very responsible application. We are doing our tests at a: Notebook DELL Latitude D600 - Intel Pentium M755 2.0 GHZ - Memory: 512 MB - VideoCard ATI Radeon 9000 32MB DDR 4xAGP - Resolution 1400x1050 - Communication: ADSL 256 kbps (Download: 45 kBps, Upload: 14 kBps) - Windows XP Professional SP1

WHERE IS THE PEER-TO-PEER?: Peer-to-peer application is that where the main function doesn't depend of a unique machine. In P2P we don't have a central main server. PCs talk to PCs. Using Squeak-Croquet, the 1st tier communication between spaces/users is a peer-to-peer application :

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