Programming Visual Basic for the Palm OS

Palm OS 4.0

Palm has recently made changes to its Web Clipping architecture that have been incorporated into the Palm OS version 4.0. Fortunately, none of the fundamentals have changed—everything we built in this chapter still works and the design principles are unaltered. Instead, Palm has added features that simplify developing an application, and that make the delivered application more powerful.

Many of the changes recognize that wireless applications are not hosted only on the Palm VII. In addition to the wireless attachments offered by other vendors, there is the Palm Mobile Internet Kit (MIK), which allows Palm OS devices to access Clipping applications using standard modems or cellular phones. The WCA viewer in Palm OS 4.0 supports color screens. In addition, there are changes that enable an application to determine other device capabilities, such as pixel depth of the Palm PDA screen in use.

One important change is that devices using the MIK do not necessarily have a unique radio ID like the Palm VII has. Instead, the Palm device forwards its serial number to the proxy server and then to your web site. Unfortunately, not all Palm devices have serial numbers! If you want the strong authentication we described earlier, and you have to support access via devices without serial numbers, you will have to encode something into the PQA itself.

The WCA viewer and Palm OS 4.0 now support cookies. Besides providing application state, cookies can often provide authentication. And ...