This topic contains the information you need to develop web applications on the Series 40 platform. Web apps for Series 40 run on mobile phones that lack the processing power and memory to run a conventional browser directly on the device. Therefore, the web browser for Series 40 devices, known as the Nokia Browser for Series 40, has two parts: the web app client and the proxy server.

Developers can create interactive applications using web standards such as XHTML, cascading style sheets (CSS), W3C widgets, and the JavaScript™ programming language. You can easily make rich, interactive pages that run well even on devices with limited resources.

Nokia Browser for Series 40 is a distributed (or proxy-based) web browser that supports full web page rendering on devices with limited processing power and memory, such as some Series 40 devices. On the phone, there is a small browser called the Nokia Browser for Series 40 Client. On a Nokia server, a larger browser application (called the Nokia Browser for Series 40 Proxy server, or simply the server) processes browsed web pages and runs web apps. The server does most of the processing for the handset client, and it communicates with websites on behalf of the client. The server sends the client optimised web page data, reduced in size to be easier to transmit to and process on the phone. The client has a JavaScript library called MWL (Mobile Web Library), which contains code to support application-like interaction on the device. MWL processing should normally be the only JavaScript that executes on the handset.

The following figure shows the Nokia Browser for Series 40 environment.

The following diagram depicts the platform stack for web applications running on the Nokia Browser for Series 40.

Figure 1. Platform stack

To simplify the task of implementing Series 40 web apps, Nokia services automatically handle several tasks. This includes the following functions:

• The server component reducing the amount of data sent to the Nokia Browser for Series 40 Client from the server by compressing images, using optimized HTML, and only sending page changes when performing web page updates

• All communication between the client browser and the Nokia Browser for Series 40 Proxy server, including session connection and the web app persistent preference storage.

• Color reduction for graphics that use a large number of colors

Creating a Series 40 web app

To create a web app, use the Nokia Web Tools. Test the app on a software phone simulator first, and then on an actual Series 40 phone. When your web app is ready to release to the public, upload it to the Nokia Store at http://info.publish.ovi.com/. Once your web app is in the Nokia Store, Series 40 users worldwide can download and use it.

Running a Series 40 web app

When a user runs a web app on a Series 40 device, the following scenario occurs:

1. The user opens a web app on the phone.

2. The Nokia Browser for Series 40 Client (on the handset) contacts and establishes a connection to a Nokia Browser for Series 40 Proxy server, asking for the particular application the user selected.

3. The web app opens on the server. If the web app has any scripts, it executes them. If the first screen of the web app requires data from the internet, the server contacts a home site or another internet data source to gather data for that first page. The app on the server prepares this data and sends it to the client. The data might include content, code for page layout and appearance, graphics, and other information.

4. The client receives the data for the first page and displays it. The user interacts with the content displayed.

5. In most web apps, the system must process user input, such as pressing a button or selecting an object on the screen. The design of the web app determines how this happens. Sometimes the client is able to process the input without help from the proxy server, but more often the client browser sends a request to the server to do some of the work.

6. The server performs the requested task and sends a response to the client. The response might be a new page or an update to the page displayed by the client. If the response is an updated page, the server sends only the portions of the page that change, not the entire page.

7. The client browser applies the changes and redraws the page.

Examples of web app processing

For examples of web app processing, see Web - Code examples on Nokia Developer.

Additional references