Ajax Patterns and Best Practices

Chapter 8. Persistent Communications Pattern

Intent

The Persistent Communications pattern provides a mechanism enabling the client and the server to communicate with each other on a persistent basis so that the client can send messages to the server, and the server can send messages to the client.

Motivation

Client-server programming, which HTTP is, requires that the client call the server to process a request. The server obliges, processes the request, and sends a response. This is a standard run-of-the-mill operation.

Now imagine writing a web application that acts like a bulletin board. Each individual has the ability to create a message and post it. One extension would be offering the capability, when the messages are displayed, to indicate whether ...