The GubcastApplet

(Client)

The Gubcast applet is the mechanism Gubcast uses to display pushed content in a frame of a given web page. Unlike most applets, Gubcast itself doesn't add anything of visual interest to your website; it's just a program that runs in the background. So it usually makes sense to make Gubcast mostly invisible by giving it the smallest possible height and width; Netscape 4.7 seems to ignore 1x1, so we recommend 2x2.

Gubcast must be correctly embedded in a page of HTML text in order to run. It only runs in the Java plug-in; the native Java virtual machines built into Internet Explorer and Netscape will not execute it. This means that you can't use the simple <applet> HTML tags to embed it, but instead must use the more complex <object> notation. (See the Gubdemo HTML for an example.)

Fortunately, Sun provides a utility program called "htmlconv" that automatically converts applet references encoded in <applet> tags to the newer standard. You can download this program here. We recommend that you write your Gubcast-enabled HTML pages using the familiar <applet> notation and then use htmlconv to convert them to the required new format.

The following Gubcast-specific parameters can be supplied in the HTML that embeds Gubcast in a Web page:

serverPort: the number of the TCP port on which the server will be listening for Gubcast client registrations. This parameter is always required.
clientPort: the number of the TCP port on which the applet must listen for connections from the server. If omitted, the next available port is chosen automatically when the applet starts. clientPort typically must be specified when the user or server is behind a firewall, so that the firewall can be directed to let TCP traffic on that port pass. [If, that is, the Gubcast operator has any control over the configuration of the firewall. When this is not the case, Gubcast cannot work across the firewall boundary.]
name: an application-specific, free-form text string that describes the client - that is, the context in which the Gubcast applet is running. Client name must be configured to give the server enough information about the client to enable it to push the right information to the user at the right time. For example, it might identify the Web page that the applet is embedded in and/or include a user account number. Defaults to "(none)"
pushsound: the name of an audio clip (.au) file defining the sound that the browser is to emit each time a Gubcast message is received by the applet. The named file must exist within the code base from which the applet itself was loaded to the browser; that is, if you don't specify the complete relative or absolute path name of the audio clip file, it must reside in the same directory as the gubcast.jar jarfile. If omitted, Gubcast message arrival will be silent.
debug: a switch that controls whether or not the applet pops up a debugging window on the user's display whenever it starts, prints diagnostic and trace information in that window as it operates, and removes the window when it stops. Debugging support is off by default. To turn it on, set debug to "yes".