Thanks a lot for your response Jeremy. I can see a lot of site that does update infos without the user to have to click "refresh" (I think Facebook does?). Do they do polling? I think this approach would be fine for me, my app if not very fast paced. Then I don't need to add a event handler to happstack-state ;)
This is done with something like: <META HTTP-EQUIV="*Refresh*" CONTENT="*n* "> ? Thanks, Corentin On Mon, Jan 17, 2011 at 5:41 PM, Jeremy Shaw <jer...@n-heptane.com> wrote: > Hello, > > The problem is that clients are not 'connected' to the web server. The way > it works (more or less) is: > > 1. client connects to server and sends a Request > 2. server sends a Response > 3. connection is terminated. > > So, once the page has been loaded there is no connection between the > web-server and the client. Hence there is no way for the server to send > anything to the clients. > > In HTML 5, there is something known as web sockets with does allow you to > have a persistent connection to the clients. However, it does not yet have > broad browser support. In fact, some browsers have temporarily removed > support due to a security flaw in the design specification. > > There are a variety of hacks collectively known as 'comet' for trying to > create a persistent connection on top of the existing HTTP 1.1 standard: > > http://en.wikipedia.org/wiki/Comet_(programming)<http://en.wikipedia.org/wiki/Comet_%28programming%29> > > That deals with trying to have the server push updates to the client. > > A different approach is to have the clients pull new data from the server > by polling the server for changes every now and then. But that depends on > how much latency you can afford for the updates. For example, if updating > only once a minute is fine versus must update every second. > > Once you decide how to get the data to the client, then you can figure out > how to track changes to the MACID database. > > - jeremy > > On Jan 17, 2011, at 4:58 AM, Corentin Dupont wrote: > > Hello again, > I have another question for happstack users/experts: > > I have a program with happstack-state and a web server with > happstack-server. > What I'd like is, whenever the MACID state is changed, that the web page is > refreshed for every clients > connected on the web server. > > So I think the question is 2 fold: > - How to add an event handler on happstack-state for that? > - How to ask to the web server to refresh every clients? > > I did not found infos about that in the API. > > Thanks a lot, > Corentin > > >
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