Application-wide Event Listener?

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ASP.NET

event

I have a page updating a table's data through ajax(json). It checks for new data every minute, so the page doesn't have to do a full postback. I think this is a lot of unnecessary network traffic. Is it possible to have an event raised from the data entry page that is listened to by the (separate) data output page?

I know HTTP is stateless and all that, is there a way to set up, like, a javascript listener that could be triggered? Something that doesn't have to check for data changes periodically, something that can be notified of a change in the data passively?

Maybe I should spend some time looking at gmail's javascript and/or HTTP requests. How does Gmail get notified to display a new inbox email?

Thanks in advance for any thoughts on this.