How to send a query to the browser from time to time?

I am creating a chat application like Messenger for the web (using the
browser) and I'm wondering if there is a way to receive new messages from
time to time from the server other than refreshing the page each 5 sec.

If there were a way to have the server-side application send new messages
to the browser this would be awesome because it would save dramatically on
bandwidth. The application would consume bandwidth only when there are new
messages. There would be no communication client-server until people write
a new message.

Do you know if it's possible?

-- 
Thanks,
Admin.
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