Hi,

We have built several systems like this where we want to push data to
clients from the server. The client is responsible for subscribing to a
channel possibly with filters in place. Rather than use GWT-RPC we have
tended to move to using raw messages that are typically json blobs. We have
used 4 basic strategies depending on the clients supported and the
application requirements. The strategies are;

1. WebSockets
2. Server-Sent Events
3. Long polling
4. Periodic Polling

I had a poke around and found a good stack overflow answer to this (See [1])

When we faced the same issues, we ended up putting together a couple
of libraries
to help with in GWT.

* websockets: https://github.com/realityforge/gwt-websockets
* Server-sent Events: https://github.com/realityforge/gwt-eventsource
* Polling: https://github.com/realityforge/gwt-webpoller (Warning this
API is not yet at 1.0 status)

The tricky part is actually managing the channels and messages sequencing
in each channel but we never got arounf to releasing our code for that part
of the problem.

HTH

[1]
http://stackoverflow.com/questions/11077857/what-are-long-polling-websockets-server-sent-events-sse-and-comet

On Fri, Oct 31, 2014 at 3:28 AM, Larry L <[email protected]> wrote:

>
> Hello,
>
> I'm new to GWT RPC. I need to write something that I subscribe on the
> client side then on the server side it can send data to client whenever
> there is update.
> As I read from the tutorial, I make a Service interface and a ServiceAsync
> interface on the client, and a ServiceImpl on the server side that
> implements Service.
>
> And then, on the client side I just call service.xxx and catch the return
> from my AsyncCallback.
> This is like I trigger the event from the client side and pull some data
> from the server side.
>
> Is there a way to "push" the data from the server side and send the data
> to every client that "subscribes" it?
>
> Thanks,
> Larry
>
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-- 
Cheers,

Peter Donald

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