How do I communicate between Applets in the same browser?

Typically, you will need some JavaScript to orchestrate the communication between applets in the same browser.

JavaScript enables flexibility and is more "top-down," or hierarchical. However, the applets can locate each other using static classes or system properties, communicating via an agreed upon object. Since classes are shared in the browser (meaning the class file is loaded once; Static fields instantiated once), you can implement a registry for an applet to locate its communicators, or a pipeFactory to return an object implementing your protocol.

Only applets from the same web server are allowed to communicate with each other. More specifically, the applets and classes must share the same CODEBASE to see each other within the JavaVM, and the MAYSCRIPT property of the APPLETtag is required to utilize the LiveConnect JSObject classes for JS related communication.