[Lazarus] Converting Pascal Client/Server application into Web Client?

[Michael Schnell]

  On 10/01/2010 02:22 PM, Michael Van Canneyt wrote:
>
> ExtJS has no such mechanism to my knowledge, but I'm not a reference.

last time I checked some months ago it was said to be a new feature, but 
should work, even though I did not find anybody who has tested it.

>
>> This is necessary to overcome the asymmetry of the http protocol.
>>
>> IMHO "Server-Events" are necessary to design a CGI program with some 
>> complexity.
>
> Well, I create seriously complex applications. No such mechanism was
> necessary till now.

Hmm, How to do notify the user that the  server has finished complex 
work in the background without blocking the interface and/or creating 
excessive http polling traffic ?

An easy to do (non complex) example for a good application for such a 
method is a server that allows tow client to chat.

>
>> Moreover "server-Internal-Events" like from Timers, serial or 
>> "direct" TCP/IP communication, thread-notification, ... are very 
>> desirable and should be able to fire "server-events" towards the client.
>
> Why ? What could you possibly need to do that the server needs to contact
> the client ? Everything you need can be programmed in the client, in my
> experience.

Above trivial example ("chat server")

Real-world: Imagine an "embedded" program automatically working with 
some hardware interfaces and/or serial and/or TCP/IP connections. Now 
you want to provide it with a "web" interface that allows a "user" to 
connect to it and do configuration and monitoring. For monitoring this 
method is essential: many "states" in the program permanently change due 
to the work of the program and the external situation. These state 
changes need to be shown in the remote browser with low latency and 
without excessive communication overhead.

>
> You must be making some very weird applications that you need such
> mechanisms :-)
I do "embedded" stuff all the time :)

-Michael