Wireless networking technology has shown an explosive growth worldwide over the past few years, bucking the general downward economic trend in the telecommunications industry. What is it about wireless networking that makes it so alluring on a grand scale? Why are there more than 75 million Wi-Fi devices worldwide, with some people projecting double that number by 2008? While marketing folks might tell you that the particular feature set and brand name of their product is driving demand, we believe the answer is much simpler: it’s magic.
Right where you are sitting now, there could be dozens of wireless data networks slinging information to the far corners of the Earth. A neighbor orders food online while someone across the street is using voice chat to talk to relatives (for free!) in Hong Kong, all the while someone upstairs is downloading a new album from their favorite band’s web site in San Francisco. The information flows all around you (and, indeed, even through you) without you seeing or hearing a thing. Make no mistake: wireless networking is probably the second most magical technology on the planet—just behind the Internet.
In hundreds of cities around the world, wireless networks are making ubiquitous connectivity more the rule than the exception, providing service (often free) to millions of users who suddenly need nothing more than a laptop and wireless card to get online. Wireless networking is getting people connected to each other more cheaply and easily than any other networking technology since the telephone.
Why Wireless Hacks?
The term hacking has a bad reputation in the popular press, where it is used to refer to someone who breaks into systems or wreaks havoc using computers as their weapon. Among enthusiasts, on the other hand, the term hack refers to a “quick-and-dirty” solution to a problem, or to a clever way to get something done. The term hacker is taken very much as a compliment, referring to someone as being creative, and having the technical chops to get things done. O’Reilly’s Hacks series is an attempt to the reclaim the word, document the ways people are hacking (in a good way), and pass the hacker ethic of creative participation on to the uninitiated. Seeing how others approach systems and problems is often the quickest way to learn about a new technology.
Wireless Hacks is about getting the most out of your wireless networking hardware and software. In this book, you will find practical techniques for extending range, increasing throughput, managing wireless resources, and generally making your wireless networking vision a reality. Remember that reality is what you can get away with, and wireless hackers have found that they can get away with quite a lot using surprisingly little. This book will show you some of the best bits of their collected experience.
How to Use This Book
You can read this book from cover to cover if you like, but for the most part, each hack stands on its own. So feel free to browse, flipping around to whatever sections interest you most.
How This Book Is Organized
This book is divided into several subjects by chapter:
- Chapter 1, Bluetooth, Mobile Phones, and GPS
The last couple years have brought hundreds of millions of tiny battery-powered wireless devices to market. Some will get you an Internet connection just about anywhere with mobile phone service, while others keep your devices connected to the “last 10 feet,” and some cover the whole globe. This chapter demonstrates some uses for these technologies, which will keep your devices (and yourself) connected, without wires.
- Chapter 2, Network Discovery and Monitoring
Wireless networking can be a lot of fun, but when it breaks, troubleshooting can be difficult without a good idea of what is really happening. This chapter will give you the tools you need to detect the presence of wireless networks, coordinate spectrum usage to avoid interference, and visualize network performance. It also covers a number of advanced data-monitoring techniques to pinpoint networking issues and even get an idea of your users’ online habits.
- Chapter 3, Wireless Security
There has been a lot of press over the last few years about the insecurity of wireless networks. In many cases, these alarmist reports are in fact absolutely true: the vast majority of wireless networks are either unintentionally left open, or worse, use unreliable security methods. This chapter explores the current standards for securing wireless networks and suggests several strong methods for protecting yourself and your wireless users from abuse.
- Chapter 4, Hardware Hacks
If it weren’t for the hardware, there would be no such thing as wireless networks. This extensive chapter tells you how to push wireless hardware to the limits, extending range and increasing performance and efficiency. It presents a large collection of components, along with sources and recommendations on how best to use them.
- Chapter 5, Software Hacks
There also would be no such thing as wireless networks without the software, which ranges from the firmware that powers wireless cards and routers to the drivers required for those cards, up to general-purpose operating systems that can be used to build your own wireless access point, router, and firewall. This chapter covers all these topics and more.
- Chapter 6, Do-It-Yourself Antennas
Since the first electrical spark was transmitted a few feet across a room more than 100 years ago, antenna design has been a fascination for wireless experimenters everywhere. This chapter presents several home-brew designs for wireless networking made by contributors from all over the world. These are practical, tested designs that can significantly extend the range of your wireless network.
- Chapter 7, Wireless Network Design
Having the equipment in place is one thing, but being able to make a wireless segment stretch for miles requires real-world experience. This chapter is a collection of techniques to help simplify the job of building wireless networks that cover the area you require.
- Appendix A, Wireless Standards
Wireless technology has not only produced impressive improvements to communications, but it has also produced an impressive list of acronyms. What is the difference between GPRS and GMRS? Which is fastest: 802.11, 802.11a, 802.11b, 802.11g, or 802.16? Exactly how do Wi-Fi and Bluetooth fit into all of this? This appendix will give you a good idea of what problems each technology is designed to solve, their relative strengths and weaknesses, and how to make the best possible use of each to fulfill your communication needs.
- Appendix B, Wireless Hardware Guide
Do you know the difference between a RP-TNC and a Reverse SMA connector? What about LMR versus Heliax antenna cabling? How do omni and sector antenna patterns differ, and why would you use one over the other? This appendix answers all of these questions and provides a comprehensive list of wireless equipment retailers.
Conventions Used in This Book
The following is a list of the typographical conventions used in this book:
Used to indicate new terms, URLs, filenames, file extensions, directories, and to highlight comments in examples. For example, a path in the filesystem will appear as /usr/local. Also used for lowercased names of programs and tools, such as tcpdump.
Used to show code examples, the contents of files, packages, modules, directives, commands, and the output from commands.
Constant width bold
Used in examples and tables to show commands or other text that should be typed literally.
Constant width italic
Used in examples and tables to show text that should be replaced with user-supplied values.
- Gray type
Used to indicate a cross-reference within the text.
A backslash (\) at the end of a line of code is used to denote an unnatural line break; that is, you should not enter these as two lines of code, but as one continuous line. Multiple lines are used in these cases due to page width constraints.
- Menu symbols
When looking at the menus for any application, you will see some symbols associated with keyboard shortcuts for a particular command. For example, to open a file, you would go to the File menu and select Open … (File → Open … ).
You should pay special attention to notes set apart from the text with the following icons:
This is a tip, suggestion, or general note. It contains useful supplementary information about the topic at hand.
The thermometer icons, found next to each hack, indicate the relative complexity of the hack:
Using Code Examples
This book is here to help you get your job done. In general, you may use the code in this book in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.
We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: "Wireless Hacks, Second Edition, by Rob Flickenger and Roger Weeks. Copyright 2006 O’Reilly Media, Inc., 0-596-10144-9.”
If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at firstname.lastname@example.org.
How to Contact Us
We have tested and verified the information in this book to the best of our ability, but you may find that features have changed (or even that we have made mistakes!). As a reader of this book, you can help us to improve future editions by sending us your feedback. Please let us know about any errors, inaccuracies, bugs, misleading or confusing statements, and typos that you find anywhere in this book.
Please also let us know what we can do to make this book more useful to you. We take your comments seriously and will try to incorporate reasonable suggestions into future editions. You can write to us at:
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