Wireless Apps: The Reality Today

Introduction
Today's Wireless environments
Multi-Device Wireless environments
Purpose of a Wireless application

Today's Wireless environments

Introduction

Development of a Wireless application does not usually require any specific procedure. This means that a number of vendors have been quick to use Wireless to promote their products, although these possess no specific Wireless feature. We could mention Allaire, for example, who proudly announced their products' support for WAP; in fact, all this turns out to mean is that a few tags have been inserted.

We will see that by using standard Web technologies, it is quite possible to set up a Wireless application.

Existing environments

The environment is the non-visible part of the application; essentially, this refers to a resource which governs much of the development and operation of the application.

The first Wireless services were grafted onto existing systems which, naturally, had not been designed to integrate Wireless technology. Wireless applications therefore often cohabited with standard Web applications, quite independently; this usually involved new developments in order to make new services available.

Environment of early Wireless applications

An example of a Wireless application

Below is a simple example of a WAP application set up in a relatively conventional Web environment:

• Web Server: Apache
• Server-side scripting language: PHP

WAP (which stands for Wireless Application Protocol) is a specification from the WAP Forum which aims to define how applications should operate within the Wireless domain. Although a gateway is essential in the WAP protocol, it is only implemented by operators. For information, the gateway works as a link between the Wireless world and the Web (translation of requests, content coders, and so on). Therefore, only the elements mentioned above are required to set up a WAP application.

Server configuration

The application server (or the Web server) needs to be configured in order to deliver WAP content. So you need to tell the server when it must make it known that the message is a WAP message. This means specifying the MIME-types (content-type) specific to WAP. For Apache, you need to edit the httpd.conf file and add the following:

The server is now able to supply WAP content. It is only essential to specify the MIME-types for static pages. Otherwise, these can be specified dynamically, as we will see later on.

Application development and testing

WAP currently uses WML (Wireless Markup Language), which is based on XML, and WMLScript, based on ECMAScript. If we compare it to a Web application, we could say that WML plays the role of HTML (document formatting) and WMLScript is like JavaScript (client-side scripting language).

Below is an example of WML:

Hello.wml

And now, here is an example of WMLScript:

Hello.wmls

To test this first Wireless application, place the Hello.wml and Hello.wmls in the Web server's root folder, and then browse the page with a WAP simulator such as that offered by Phone.com (now OpenWave).

YoSpace Emulator

The above picture shows the result that you should then obtain. As long as your server is accessible via Internet, you should be able to access your application using any WAP phone. All you need to do is enter the relevant URL to access the resource.

We will now put together a dynamic application which generates WAP content on the fly. We will use PHP to do this. Of course, it is equally possible to use any other technology to dynamically generate documents (ASP, JSP…). Below is the source code for our example:

Hello.php

It is crucial not to omit the Content-Type information from the header. It is this information that enables the different agents in the protocol to correctly process the message (gateway, browser…). The rest of the code is conventional — you insert the PHP code inside the WML code. You can therefore carry out any processes you want (database access, image generation…).

Recap

From this rudimentary example, we can see that it is possible to build any Wireless application. But as we have already mentioned, the present case involves redeveloping applications. And since, as we know, you need one version for HDML, one for WAP, another in HTML 3.2 for PDAs, and so on, it is clear that development and maintenance costs will quickly begin to add up.

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