The lack of synchronous communication leaves us in a very unsatisfacory situation. Therefore, the primary rationale of this project is to create an appropriate mechanism. We create a Java applet which realizes synchronous communication generically and establish a protocol to use it. This way, an implementation independent interface for both client and server side will be defined.
All this must be supported by a server side infrastructure. I choose to use PHP (version 4) because it is well established and quite powerful, and of course, for my own convenience. It should not be a major challenge to implement the same functionality with say Microsoft's ASP.Net technology or Perl. In deed, this functionality could even be implemented as a module of an HTTP server. Therefore, my primary goal is not the implementation (consider it just a proof of concept) but the definition of an interface to separate functionality from implementation.
If you like these ideas come on and continue reading. What I present here corresponds to my proper experience. Now I think it's worth discussing within the community, to see if the needs of others could be satisfied as well. Your comments are welcome!
One more remark: The project is still under construction which means that all the pages here are being continuously reworked. So it may happen at some point of time or another that a piece of code fails to exute successfully. I'm committed to remedy such situations as soon as possible.
As of May 2003, the pages presented here are not any more very up to date. I tested my implementation with several browsers including IE 6.0, Opera 8.0, Mozilla 1.71, Firefox 1.03. I found a couple of incompatibilities between these browsers and fixed some bugs. Everything appears now to work fine. (Apart from the fact, that Firefox regulary crashes eventually - which it does whenever it loads a Java applet as simple this might be - and to a lesser degree also Mozilla. Since this behaviour occurs independently of this project on every machine I tried - all WindowsXP based - I decided to not consider this a bug of my implementation. Opera and IE run absolutely stable. However I replace the Java applet with some more or less browser specific constructs such as HTTPRequest and XMLHttpRequest wherever possible; apparently Firefox and Mozilla run more reliably this way. Opera's version 8 does not yet implement all the necessary methods of XMLHttpRequest - that is why we're still using the Java applet here.). So the next thing is to update these pages and to port them to the dataPort technology. Stay tuned! A first demo can be viewed here.
The material presented here is being considered to be put under a public license; however, no decision has been taken yet. Therefore, the following applies:
Clearly, this material is based on the work of others. Where appropriate, the author has tried to indicate sources wherever possible. Failure to do so does not mean that the author claims his authorship for the material in question. However, he claims authorship for all the material contained herein which has not been published elsewhere by others before. This material, called "material" in what follows, is subject to the following conditions:
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© 2005 Goetz Heller, Dr.Heller Information Management
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