The reading assignment for Thursday is Stein's chapter 2 (Unraveling the Web). Although we've covered parts of it before we will revisit now in the context of Java networking & CGI.

This week we'll want to build a web feedback applet that sends e-mail to the webmaster of the site it's on. Very much like the feedback CGI script that we have covered last week.

We'll see that we need to create our own (primitive) GUI. Then we will choose to send the data to a CGI perl script that will do the mailing for us.

To understand how this can be accomplished we will need to revisit briefly the HTTP protocol and the basics of CGI with POST and to discuss how Java sends and receives data across the network.

So that this latter part be clear we will start by writing a small network client, and then a simple server (that lets you type lines to it, and sends them back to you afterwards).

When our feedback applet is done we would have seen a simple GUI in Java (that we could then compare with our GUI up to now, HTML forms) and would have seen how data can be sent over the network to a CGI script in much the same way the browser does it from an HTML form.

Of course, there are other ways in which a Java applet or application can send an e-mail message, and we'll briefly explore alternatives.

The GUI that we will build for this lecture's example will be very simple on purpose. More sophisticated approaches will be mentioned briefly as well.

The next topic then, next week, will be the GD.pm module that lets us create GIF files from CGI scripts, and we will develop a graphical but crude web counter with CGI.pm and GD.pm. CGI.pm and GD.pm are very useful programming tools for those doing CGI programming.


Lecture notes for Thursday will be posted here tonight, Wednesday the last day of September 1998, very late at night.