How to update a portion of a page in near-realtime?

[CptDondo]

OK, let me explain what I am trying to do.

I have an embedded PC that runs a httpd+php server and controls a machine.

I have a browser front end that provides the HMI (human machine
interface) to the machine.

The machine has about a dozen status indicators; things like over-temp,
powerfail, and so on.

I've been asked to provide a status page that shows the status of these
indicators in near-realtime, say current to within a second or so.

In order to update these indicators, the embedded PC must query another
controller. So the sequence is this:

Browser says, time for new update; queries backend.
Backend launches the query program, which requests status from other
controller.
Other controller responds with current status (about 16 bits of data).
Query program provides this information back to the originating program.

I cannot update the entire page, as part of it is a flash movie that
takes something like 30 seconds to generate on my embedded platform. I
need to update only < 16 icons on one small portion of the page.

What is the best way (or simplest, or lightest in resources) to do this?
I need something portable that can work with different browsers.

Thanks,

--Yan

[Dag Sunde]

CptDondo wrote:

OK, let me explain what I am trying to do.

I have an embedded PC that runs a httpd+php server and controls a
machine.
I have a browser front end that provides the HMI (human machine
interface) to the machine.

The machine has about a dozen status indicators; things like
over-temp, powerfail, and so on.

I've been asked to provide a status page that shows the status of
these indicators in near-realtime, say current to within a second or
so.
In order to update these indicators, the embedded PC must query
another controller. So the sequence is this:

Browser says, time for new update; queries backend.
Backend launches the query program, which requests status from other
controller.
Other controller responds with current status (about 16 bits of data).
Query program provides this information back to the originating
program.
I cannot update the entire page, as part of it is a flash movie that
takes something like 30 seconds to generate on my embedded platform. I
need to update only < 16 icons on one small portion of the page.

What is the best way (or simplest, or lightest in resources) to do
this? I need something portable that can work with different
browsers.

Near realtime? Well...

Look to AJAX and its related teqniques... (as long as the client
browsers have JS enabled) to get the status from the server.

Then use the response from the AJAX call together with the DOM,
or .innerHTML to update parts of the page.

--
Dag.