Comet Programming

Comet is a Web application model that enables web servers to send data to the client without having to explicitly request it. Developers can utilize Comet techniques to create event-driven Web apps. Comet is actually an umbrella term for multiple techniques for achieving client-server interaction. All methods have in common that they rely on browser-native technologies such as JavaScript, rather than on proprietary plug-ins

In theory, the Comet approach differs from the original model of the web, in which a browser requests a complete web page or chunks of data to update a web page. However in practice, Comet applications typically use Ajax with long polling to detect new information on the server. The concept predates the coining of the neologism, and is known by several other names, including Ajax Push, Reverse Ajax Two-way-web, HTTP Streaming and HTTP server push among others.