COMET is a Web application model that enables web servers to send data to the client without having to explicitly request it. Developers can utilise 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.

COMET uses a persistent connection between the client (Web Browser, using XmlHttpRequest) and the server. This persistent connection is held open on the server for a predefined period of time and will only respond back to the client with either a timeout message, or when some part of the server's application logic wants to send a message. Once the client receives the message, it is processed using the application logic implemented on the client. The persistent connection is then reopened, and the process starts again.

A second connection is used to send messages to the server; this connection is not persistent, and typically returns immediately after it is processed.

Testing COMET applications can be achieved easily using NeoLoad. Click Here to request an online demonstration of NeoLoad.