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Writing networked applications is one of the most interesting aspects of programming. This is especially intriguing when you see your applications successfully communicating over the network. In this chapter, you will build a chat application that works similarly to Windows Live Messenger (or ICQ) using TCP/IP. Using the chat application, you will learn how network programming happens in .NET and the various challenges you’ll encounter when building a multiuser chat application.

Serial communication is one of the oldest mechanisms for devices to communicate with each other. Starting with the IBM PC and compatible computers, almost all computers are equipped with one or more serial ports and one parallel port. As the name implies, a serial port sends and receives data serially, one bit at a time. In contrast, a parallel port sends and receives data eight bits at a time, using eight separate wires.

Biometric recognition is one of the most reliable ways to confirm the identity of an individual. And by now, most people should be familiar with the Microsoft Fingerprint Reader (http://www.microsoft.com/hardware/mouseandkeyboard/productdetails.aspx?pid=036; see also Figure 3-1).

With all the buzz around WiFi, Bluetooth, and other wireless technologies, it’s easy to overlook one of the simplest and most common forms of wireless communications—infrared. Anyone who has ever used a remote control has used it! Infrared uses the invisible spectrum of light just beyond red in the visible spectrum. You can use it in applications for short-range, point-to-point data transfer. Because it uses light, line-of-sight is a prerequisite for infrared. Despite this limitation, infrared is increasingly popular in devices such as digital cameras, PDAs, and notebook computers.

Radio frequency identification (RFID) is one of the buzzwords receiving a lot of coverage in the IT world lately. An RFID system is an identification system that uses radio waves to retrieve data from a device called a tag or a transponder . RFID is all around us in our daily lives—in the supermarkets, libraries, bookstores, and so on. RFID provides a quick and efficient way to collect information, such as stocktaking in a warehouse or tracking of the whereabouts of items.

Today, a webcam is a common peripheral that most people can easily afford; and it’s used most often for video conferencing. But what can you do with your webcam besides video conferencing? For .NET developers, the answer is plenty; and you will be glad to know that integrating a webcam with a Windows application is not as difficult as you might imagine.