The Applet
The applet is for those people that provide terminal
based services and would like to add web capabilities to it.
The applet is the perfect way to make the transition from a terminal based
system to a more sophisticated web based framework easier. To bring the
terminal based application on the web one need to allow telnet or ssh access
to it (which usually already exists) and then set up the Applet on a page
on their web server. A second interesting usage is to set the applet up
on your private home page and use it to be able to log in from remote
locations without the need for any communication programs except a
Java capable web browser.
Quickstart
To quickly have the applet up and running following
the steps below:
-
Copy one of the examples in the html
directory (AppletTest.html
or AppletEnhanced.html)
to the directory on your web server where you would like to install the
applet.
-
Copy the jta20.jar
file to the same directory on your web server.
-
Edit the file you copied in step number one!
Look for the applet tag, set the CODEBASE
to
"." and remove the jar/ from the archive file
name.
Make sure it looks like the following piece
of HTML text:
<applet CODEBASE="."
ARCHIVE="jta20.jar"
CODE="de.mud.jta.Applet"
WIDTH=590 HEIGHT=360>
... some more configurations but not
essential now ...
</applet> |
-
Important: There is a problem with Netscape
that forces you to put the defaults.opt file
in the same directory as the jar and the html file. Simply download defaults.opt
and put it there.
-
Verify that all files (html and jar) are readable
for all users, so that the web server can handle them.
-
Go to the page AppletTest.html on
your web server. It should load the applet and prompt you with your telnet
login. If you have a problem check the files
again and have a look at the Java console of your web browser to find out
what the problem is. In case you still do not understand what is going
wrong have a look at our FAQ and next write
to us, but include a copy of your java console contents.
Applet Parameters
The new version of the software tries to reduce the amount of parameters
that you have to change to make the applet work. Instead of using these
applet parameters it uses a configuration file now. Which file to use is
determined by a parameter however.
Before we go into more detail on the applet parameters lets take a look
at the <applet> tag in general. The example files (see documentation)
usually contain a piece of html text like the following:
-
<applet CODEBASE="../"
-
ARCHIVE="jar/jta20.jar"
-
CODE="de.mud.jta.Applet"
-
WIDTH=590
HEIGHT=360>
-
<PARAM NAME="config" VALUE="http://server/applet.conf">
-
<!--
-
Make sure
the config value is a valid URL.
-
The file
applet.conf looks just like defaults.opt.
-
applet.conf
overrides settings in defaults.opt!
-
-->
-
</applet>
<applet CODEBASE="../"
The first line contains the CODEBASE attribute
which points to the directory where the jar archives are located. This
is necessary as the example html files are in a different location. So
if you put the jar files in the same directory as your applet html file
you may set this to "." or simply remove the whole attribute.
ARCHIVE="jar/jta20.jar"
The next line contains the actual archive that is
used to get the classes from. Using a jar archive drastically reduces the
download time for the applet. In our example the jar archive rests in a
directory jar/ and you need to remove that directory part if you
placed the jar file in the same directory as the html file.
CODE="de.mud.jta.Applet"
The third line tells the browser which class to load
as the applet. You do not need to change anything here.
WIDTH=590 HEIGHT=360>
The last line of the opening <applet>
tag tells the browser how big to make the applet. In our example it has
a width of 590 pixels and a height of 360 pixels. Adapt this according
to your needs. In general the applet adapts its font size to match the
size of the applet.
Everything else will be explained below and finally you need to close
the applet definition using the </applet> tag.
The parameter format is <PARAM NAME="name" VALUE="value">
and has to appear within the <applet> and </applet>
tags.
| Parameter |
Documentation |
NAME="config"
VALUE="URL to configuration file" |
The parameter points to the configuration file for the applet. It may
be either a path relative to the CODEBASE or a fully qualified
URL.
This parameter replaces all following parameters
that had only been implemented for convenience. |
NAME="plugins"
VALUE="pluginlist" |
(deprecated, use the config file)
Use this parameter to define a different list of plugins to be loaded on
startup of the application. Plugins are always added from back to front
and are separated by comma:
Socket,Telnet,Terminal
The above pluginlist is the default. No whitespaces are allowed! |
NAME="layout.plugin"
VALUE="direction" |
(deprecated, use the config file) If a
plugin is a visible component you can define where it will appear on the
screen. At the moment only BorderLayout directions are understood.
So you may place plugins at the Center, North,
South,
East
and West. Usually you want to place the Terminal
plugin in the center! |
NAME="port"
VALUE="port number" |
(deprecated, use the config file) Use
this parameter to set a different port than 23. This may be necessary for
the SSH plugin. |
|
To
use the applet keep in mind, a few of the following hints:
| Java
Security |
| Java Applet are only allowed to connect back to the server, where the
classes where loaded from. So you need a web server on the computer where
you want to log in. However, using our relayd
program on your web server you can log into other hosts as well.
Another way is to use a signed applet. But this must be done differently
for Netscape and other browsers. |
| Without a
Web Server |
| People sometimes try to load the html pages without a web server
from their local hard disk. This may work or it may not, as some security
manager implementations do not accept local hard disks as a secure source
for classes. |
|