Book Image

Learning Network Programming with Java

Book Image

Learning Network Programming with Java

Overview of this book

Network-aware applications are becoming more prevalent and play an ever-increasing role in the world today. Connecting and using an Internet-based service is a frequent requirement for many applications. Java provides numerous classes that have evolved over the years to meet evolving network needs. These range from low-level socket and IP-based approaches to those encapsulated in software services. This book explores how Java supports networks, starting with the basics and then advancing to more complex topics. An overview of each relevant network technology is presented followed by detailed examples of how to use Java to support these technologies. We start with the basics of networking and then explore how Java supports the development of client/server and peer-to-peer applications. The NIO packages are examined as well as multitasking and how network applications can address practical issues such as security. A discussion on networking concepts will put many network issues into perspective and let you focus on the appropriate technology for the problem at hand. The examples used will provide a good starting point to develop similar capabilities for many of your network needs
Table of Contents (16 chapters)
Learning Network Programming with Java
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Using a selector


A selector is used in an NIO application and allows one thread to handle multiple channels. The selector coordinates multiple channels and their events. It identifies those channels that are ready for processing. If we were to use a thread per channel, then we will find ourselves switching between threads frequently. This switching process can be expensive. Using a single thread to handle multiple channels avoids some of this overhead.

The following figure depicts this architecture. A thread is registered with a selector. The selector will identify the channels and events that are ready for processing.

A selector is supported by two primary classes:

  • Selector: This provides the primary functionality

  • SelectionKey: This identifies the types of events that are ready for processing

To use a selector, perform the following actions:

  • Create a selector

  • Register channels with the selector

  • Select a channel for use when it becomes available

Let's examine each of these steps in more detail...