Raspberry Pi Server Essentials: If you want to use Raspberry Pi as a server, this is the book that makes it all possible. Covering a wide range of projects – from network storage to a game server – you'll learn in easy, engaging steps.

As of the time of writing this book, the current Raspbian image supports a variety of wireless adapters—without the need to install any extra drivers. Many of the mini, nano, or micro versions run directly off the Pi's USB ports and do not require a power USB hub.

Because the Pi is limited to two USB ports, it might be wise to have a compatible, powered USB hub. Powered being the key word here, as this will allow you to plug in any USB device or several devices at the same time without affecting the Pi's power stability. As of this writing, Raspbian is not fully compatible with USB 3.0 hubs yet.

Most wired keyboards and mice will run directly off the Pi (since Revision 3). Many Bluetooth keyboards and mice also work directly off the Pi's USB ports, but require initial setup using a wired keyboard. Some wireless keyboards, such as the Microsoft 3000 series, do not need any configuration as they emulate a wired keyboard and can be used during boot time.

You can connect to the worldwide network by using a 3G dongle. These require a lot of power, and they need to run from a powered hub to operate at full speed. But, they are a really easy way to connect your Pi to the Internet, even in the most remote places of your country. As long as you have the basic voice signal, you should always be able to use GPRS (single channel 57.5 KBps or dual channel 115 KBps). This can be enough to send plenty of logging data as text. Some countries offer free text messages, and these can also be used to send and receive a minimum amount of data. If you plan to run a server, it would be recommended to use LAN or Wi-Fi connected to an ADSL/DSL connection instead.

The Pi has its own sound hardware, which is really good at giving you high definition sound over HDMI or analog sound via its RCA connection (you cannot use both). You might find yourself in a situation where you would like to record audio from a line input or a microphone; you could then use any USB 1.1 or USB 2.0 device.

Infrared (IR) receivers are a great way to control your Pi using conventional remote controls. The FLIRC USB IR remote dongle is a great way for you to start doing this.

This is the ultimate way to turn your Pi into a full DVR system. You can record, playback, or pause live TV from HD satellite or Digital TV. You can also listen to your favorite radio channels.

The Pi has a port for its own dedicated HD camera module. Owning one of these cameras is a real treat, but they do not have proper V4L (Video for Linux) support like most USB cameras. This means that doing some easy tasks can be much more complicated. There is a chapter dedicated to this later in the book.

These come in handy if you work with various types of cards. There is limited support on the generic types; but, the USB 3.0 USRobotics all-in-one card works really well, and you can mount all six cards at the same time.

WyoLum is a startup business that creates useful add-ons for various applications. Specifically, the AlaMode is an Arduino-compatible board with a real-time clock and microSD slot that sits on top of the Pi. You can communicate with Arduino using the Pi's dedicated Universal Asynchronous Receiver/Transmitter (UART), and it can run on the Pi's power source. If you like electronic projects and are already familiar with Arduino, this is worth looking at. You can even use it to flash other Arduino compatible chips or upload firmware to run it on its own!

Though you may not like to downgrade from HDMI to VGA, you can purchase inline HDMI to VGA converters from your favorite online auction shops or electronic stores. You must make sure that you buy an ACTIVE converter, which is slightly more expensive than the passive converter. Active means that it contains a microcontroller that uses power from the HDMI port to convert the digital signal into the VGA standard. The Raspberry Pi is capable of powering these types of devices.

Microsoft's Xbox 360 controller works as a mouse in X using the Arch Linux distribution. Other joysticks might need a ported driver that can be found on Internet forums.

You can purchase simple USB to SATA controllers that allow you to attach SATA hard drives by using the dedicated power supplies. The real fun begins when you use hardware RAID-based USB to SATA controllers that can be chained in various configurations. This can give you massive storage, high redundancy, and maximum performance. Be careful though, as the maximum throughput speed you can achieve is governed by the bandwidth of USB 2.0. In theory, this is a maximum speed of 60 MBps; but it is shared by all the devices on the controller and not per port. There is more information on this later in the book.

The CAN bus is the standard used in all modern motor vehicles. It is a standard port that gives mandatory data that can be interpreted by anybody. For example, throttle value, misfiring of cylinders, or air to fuel ratio. PEAK-System has a variety of peripherals and software that are compatible with the Pi. If you have access to the manufacturer-specific codes, you can even adjust engine mappings with these tools.

A compatible device called TellStick runs well as a third-party home automation device for the Pi. But as an advanced Linux user, you should strive to make your own applications; the best add-on for this is the AlaMode from WyoLum.

Available from a variety of websites and stores, this is the perfect gadget if you need to shoot plushy missiles at unidentified objects! This is purely an entertainment peripheral, but you could use it for DIY projects.

Futronic's fingerprint scanners work well with Raspbian, and there are many examples that can be found online. They are standalone programmable devices that communicate with the Pi using simple messages over USB-UART, and have extensive documentation available with the device.

It may be disappointing that the Raspberry Pi foundation decided to use a 100 MBps LAN chip instead of a gigabit one. But, we need to crunch some numbers to justify this decision. Let's convert megabits to more familiar megabytes. To get to "megabytes per second" from "megabits per second", we divide 100 MBps by 8 (there are 8 bits in a byte). This equates to 12.5 megabytes per second at 100 percent LAN capacity. For a single user, this is only roughly 20 percent of what the USB hub can handle. That means that, by design, this is an unchangeable bandwidth limitation for networking.

If you plan to share files with several users at the same time, each new user will bump down the other user's bandwidth to accommodate their own. As a work-around, you could add a gigabit USB LAN peripheral to increase the bandwidth. But, due to the speed constraints of the USB hub, you will only use approximately 48 percent of the gigabit LAN. To make matters worse, the hard drives running on the USB port will start to fight for bandwidth. The USB Controller has to share 480 MBps across all the four ports! One port is used by the 100 MBit network card, and the other connects the hub to the GPU. For one user, this means a maximum bandwidth of 240 MBps. Why 240 MBps? This is because 240 MBps goes to LAN and 240 MBps goes to the hard drive; and theoretically, there is no USB bandwidth left for anything else.

This can be a problem for a multiuser environment, but for home use, you would not run into any major problems as the bandwidth can accommodate HD video streams while serving other clients. This is why the cheaper 100 MBit version was used.

As it was made clear by the bottlenecks found with LAN, the worst thing about USB bottlenecks is that there is no way to work around this problem! This is because the USB Controller connects to the Broadcom chip and the LAN chip on the PCB, without any possibility of expanding or replacing this chip.

The Pi does not come with a real-time clock, so timekeeping is left to Internet-based time servers. For most people, this might not cause a problem. But if you want to create a remote, disconnected device that depends on events that are recorded at various times of the day, you might be left a little bewildered.

One easy and reliable way to do this is to connect a USB or I2C RTC that runs on a small battery. There is an easier and free option though, but it is not as accurate. You may want to install the fake-hwclock package. All you need to do is set the time once and the software will keep track of time by using a file. If you have a power outage, the software will read the file and set the time back to the last known time. The drawback is that you lose that time as there is no way to determine how long the outage lasted.