Obtaining Wireless News with J2ME and PHP

he Java 2 Platform, Micro Edition (J2ME) is targeted at cell phones, smart cards, pagers, and other consumer devices. J2ME technology consists of a virtual machine and a set of APIs suitable for tailored runtime environments for these devices. PHP, on the other hand, is a widely used server-based language to build Web applications. But these two radically different technologies work very well together. In this article you’ll see how they can interact via HTTP (Hyper Text Transfer Protocol). Of course, this is not intended to be a thorough explanation of how HTTP works?you only need to know that HTTP is a request/response protocol. That simply means that the client application performs a request and the server application returns a response.

Figure 1 illustrates a typical HTTP-based Client/Server communication. In this case, the client requests the latest news to a Server sending it the type of news wanted. The Server simply responds to the Client sending it the news requested.

You understand then, that as long as client and server “speak” the same protocol they can communicate without problems. HTTP is the ad hoc protocol for our purposes. In fact, HTTP doesn’t specify which entity is supposed to be either the client or the server. The client can be a Web browser, a mobile device, or anything else, provided that the applications on both ends can communicate through HTTP. For example, suppose you write something like this in PHP:

Figure 1. Client/Server Communication: The figure illustrates the process by which a client requests and receives news from a server.

   echo "Hello World";

The result depends on the client performing the request. If the client is a Web browser then it will display the string “Hello World.” If the client is a mobile phone it will just receive the string “Hello World” as a stream of bytes from the server.

The point is that it’s not hard to get a mobile device, running J2ME to communicate with a server running PHP as long as both use the HTTP protocol.

A Sample Project
As I’m sure many of you developers out there are, I’m fed up with parsing RSS feeds to get information and links. RSS feeds are nothing more than XML files with a particular structure. They are used mainly to represent a set of items published on a Web site. Here’s an RSS feed excerpt:

   ...