comet, cometd, twisted, and websync

I am confused about comet, come开发者_JAVA百科td, twisted, and websync. What is the difference?

Comet is the technology itself (=allows to get and send requests from JS asyncroniously without very little overhead).

Cometd/twisted/Websync are specific implementations, applications which serve requests through comet.

In addition to BarsMonster's answer; Comet Ajax(Reverse Ajax) refers to an Ajax design pattern that uses long-lived HTTP connections to enable low-latency communication between a web server and a browser. (Wikipedia 2010)

Some of the reliable implementations are;

• DWR (Direct Web Remoting - Java )
• PokeIn ( PokeIn Reverse (Comet) Ajax Library - .Net & Mono )