The COMAL Servlet

Suitable hardware platforms

We have now tested the WebCOMAL package on various PCs ranging from 90MHz Pentium Classics up to 400MHz Celeron processors, and across two small Local Area Networks. The package runs very smoothly and responds quickly on them all, with only normal delays of a few seconds between posting data in the browser and the results being delivered back to it. During tests on an Intel P166 machine connected to 19 others on a school 10 Mbit network, there was a longish delay between clicking on the HTML link and the results from the COMAL program appearing. We don't yet know why the performance suffered so much on this network, and we will investigate this further.

What software components do you need?

If you are running UniCOMAL V3.11 from inside MS-Windows 95 or 98, it is likely that you have most of the software components already available on your system. Here is a complete list:

• UniCOMAL V3.xx, Students' or Developers' Editions
• WebCOMAL03, the Servlet package developed by P&D Software
• JDK 1.2.2, the Java Development Kit, available from Sun Microsystems - or at least JRE 1.2.2
• a Java-aware Browser, MSIE 4 or higher, or Netscape Communicator
• the TCP/IP networking protocol supplied with MS-Windows 95 or 98

How do you get hold of the components?

How to get started

First, you need to install the Java Development Kit JDK 1.2.2. The rest of this project assumes a default Java Installation, that is, the Java Runtime Environment (JRE) is installed to the folder C:\Program Files\Javasoft\jre\1.2\. We strongly recommend that you install JDK in this way, because, if your JAVA installation is different, you will have to change all the paths in the WebCOMAL package to point to where the JAVA components are, and this is tricky to do and prone to error.

Next, you need to unzip the WebCOMAL files to a WebCOMAL folder inside your C:\COMAL or C:\STCOMAL folder on your hard drive. Once again, the setup assumes a default UniCOMAL Developers' installation, so if you are using UniCOMAL Students', you will need to change some details in the startup file. More about that later. Full details on which files need to be copied to which folders on your system, are contained in the README.TXT file in the WebCOMAL03 distribution.

Third, you need to make sure that the MS-Windows Network components are installed on your PC, and that the TCP/IP network protocol is available. This is done by clicking Start > Settings > Control Panel > Network > Add > Protocol > Microsoft > TCP/IP. You will be asked to insert your MS-Windows distribution media.

Next, you need to run the file startcs.bat (from the WebCOMAL folder) so as to activate the Java Servlet which sets up the link between your browser and the UniCOMAL interpreter. After running this file, you should have a DOS window with the Servlet messages displayed in it, like this:

C>SET JRE=C:\Progra~1\javasoft\jre\1.2

C>SET LIB=C:\Progra~1\javasoft\jre\1.2\lib

C>
C>SET CLASSPATH=.\java\classes;.\java\lib\jsdk.jar;C:\Progra~1\javasoft\jre\1.2\
lib\rt.jar;C:\Progra~1\javasoft\jre\1.2\lib\jaws.jar;C:\Progra~1\javasoft\jre\1.
2\lib\i18n.jar

C>
C>
C>C:\Progra~1\javasoft\jre\1.2\bin\java.exe -cp .\java\classes;.\java\lib\jsdk.j
ar;C:\Progra~1\javasoft\jre\1.2\lib\rt.jar;C:\Progra~1\javasoft\jre\1.2\lib\jaws
.jar;C:\Progra~1\javasoft\jre\1.2\lib\i18n.jar comal.ServletServer -d .\java\cla
sses -p 8080
servletrunner starting with settings:
  port = 8080
  backlog = 50
  max handlers = 100
  timeout = 5000
  servlet dir = .\java\classes
  document dir = .\examples
  servlet propfile = .\java\classes\servlet.properties

This Servlet runs, in the background, during the interaction of the Browser with COMAL. Messages relating to the running program, including any error messages, are displayed in this Servlet window.

Now you are ready to launch your browser by double-clicking on one of the example HTML files supplied with the system, such as WebCOMAL.HTML for example. When launched, each example HTML file contains a link which launches a UniCOMAL program from the browser.

The sample programs

WebCOMAL03 comes with a small collection of sample programs illustrating some of the possibilities of the new system. Each COMAL program is called from an HTML script allowing the program to be launched from the browser. This table shows what they each do:

Path names and Students' COMAL

The 'startcs.bat' file starts up the COMAL servlet. To do this it first assigns values for the path names to locate the Java Runtime Environment. Here is an example, for a standard JAVA system:

  SET JRE=C:\Progra~1\javasoft\jre\1.2
  SET LIB=%JRE%\lib

  SET CLASSPATH
  =.\java\classes;.\java\lib\jsdk.jar;%LIB%\rt.jar;%LIB%\jaws.jar;
  %LIB%\i18n.jar

  rem # Run the Servlet
  %JRE%\bin\java.exe -cp %CLASSPATH% comal.ServletServer -d   .\java\classes -p 8080

Once the proper paths to the JAVA side of the system are set up, the HTML files which call the COMAL programs must also point to the correct locations for the COMAL environment. For Students' COMAL, this will normally be C:\STCOMAL\. So, for example, in the test.html file, the proper code for use on a Students' COMAL system should be:

a HREF =http://localhost:8080/servlet/comal.ComalServlet?COMAL_EXE=
c:\stcomal\comal.exe&COMAL_PRG=c:\stcomal\samplet.cml