Hardware Reference
In-Depth Information
When you connect to the network, a DHCP request is initiated with the router
that allows the router to dynamically assign you an available IP address. This
makes network setup much easier because you don't have to know about your
network configuration to connect to it. However, it can make talking to your
Arduino a bit tougher because you need to find out what IP it was assigned.
DNS
DNS stands for Domain Name System. Every website that you access on the
Internet has a unique IP address that is the location of the server on the web.
When you type in
www.google.com
, a DNS server looks at a table that informs
it of the IP address associated with that “friendly” URL. It then reports that IP
back to your computer's browser, which can, in turn, talk to Google's server. DNS
allows you to type in friendly names instead of remembering the IP addresses
of all your favorite websites. DNS is to websites as your phone's contact list is
to phone numbers.
ClientsandServers
In this chapter, you learn about how to use the Ethernet shield to make the
Arduino act as either a client or a server. All devices connected to the Internet
are either clients or servers, though some actually fill both roles. A
server
does
as the name implies: When information is requested from it, it serves it up to
the requesting computer over the network. This information can come in many
forms; it could be a web page, database information, email, or a plethora of other
things. A
client
is the device that requests data, and obtains a response. When
you browse the Internet from your computer, your computer's web browser is
acting as a client.
NetworkingYourArduino
For all the examples in this chapter, you use your Arduino paired with the
official Arduino Ethernet shield. There are multiple revisions of this shield, but
these examples are tested to work on the most recent version of the shield with
the WIZnet Ethernet controller chip. Significantly older versions of the shield
used a different chip, and are not guaranteed to work with these examples. You
may also use the Arduino Ethernet, a single-board Arduino that combines the
Ethernet connectivity on to the Arduino board.
TIP
IhavefoundthattheEthernetshieldworksmorereliablythantheArduino
Ethernet.
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