CSCI A348/A548
Lecture Notes 29

Fall 1999

Diagram of the web chat application and homework 9 hints.

Here's the diagram of homework 8 with sinks and source:

In this diagram Larry types 'Yo!' which is being then propagated to both clients, already waiting to display what's being said in the chat room. The transfer is done through the source, into the sinks. As soon as the sinks return the results, the client applets display the string and issue a new GET request. Meanwhile, in a separate thread, the applet monitors the text field in which the users can type their messages.

We've covered applet-servlet communication in this last part.

We said there are three options:

HTTP
sockets
RMI

We've exemplified the first and the last.

Sockets are used somewhere much earlier in the lecture notes.

RMI is

elegant
allows callbacks
working through firewalls

RMI also is

complicated to set up
supported by few browsers
Java-based

HTTP is

easy to write
working for applets running behind firewall
allowing Java applet to communicate to any program in any language
JDK1.0-based
allowing for encrypted (https) communication
leveraging existing CGI programs

HTTP also is

slow
relying on awkward url-encoded strings
forcing responses to follow similar constrains
not allowing for callbacks

For homework 9 please use the notes you took in class, or lab notes 15, or send me a message or come to office hours.

Last updated: December 10, 1999 by Adrian German

CSCI A348/A548 Lecture Notes 29

CSCI A348/A548
Lecture Notes 29