Comet programming

Comet is a web application model in which a long-held HTTPS request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term, encompassing multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as JavaScript, rather than on non-default plugins. The Comet approach differs from the original model of the web, in which a browser requests a complete web page at a time.

Long Polling: The client sends a request to the server, which holds the request open until data is available or a timeout occurs. The client then immediately sends another request upon receiving a response.

Comet: A broader term that can encompass multiple techniques for achieving real-time updates from the server to the client, including long polling.