Options for Communicating in Local Networks
and on the Internet
by Jan Axelson
If you have a device that you want to use in a local network or on the Internet, one of the decisions you’ll need to
make is how the device will exchange information with other computers in the network. Many devices host web
pages that display information and enable users to send input, but web pages aren’t the only option.
Other choices include Email, File Transfer Protocol (FTP), and custom applications that use lower level Internet and
This article explores the possibilities, including how to decide which option is best for your project. The focus is on
solutions that are practical for small systems, but the information also applies to PCs that perform monitoring and
control functions in networks.
If you have a project that involves putting a device
on a local network or the Internet, one decision you’ll
need to make is how the device will exchange
information on the network. Even for small devices,
there are more options than you might think.
A device can host web pages, exchange Email
and files, and run custom applications that use
lower level Ethernet and Internet protocols.
This article will help you decide which protocol
or protocols best suit your application. The focus is
on options that are practical for small systems, but
the information also applies to PCs that perform
monitoring and control functions in networks.
The Basics of Networking
Computers can use a variety of protocols to
exchange information on a network. Each protocol
defines a set of rules to perform a portion of the job
of getting a message from one computer to the
program code that will use the message on the
destination computer. For example, the Ethernet
protocol defines (among other things) how a
computer decides when it’s okay to transmit on the
network and how to decide whether to accept or
ignore a received Ethernet frame.
Other protocols can work along with the
Ethernet to make transmissions more efficient and
reliable, to enable communications to travel beyond
local networks, and to provide information that a
specific application requires. For example, every
communication on the Internet uses the Internet
Protocol (IP) to specify a destination address. Table
1 shows protocols that many small systems support.
Multiple networking protocols work together by
communicating in a layered structure called a
stack. The lowest layer is the Ethernet controller or
other hardware that connects to the network. The
top layer is the end application, such as a web
server that responds to requests for web pages or a
program that sends and requests Email messages.
Figure 1 shows typical layers in a networking
stack. Not every computer needs to support every
protocol. Small devices can conserve resources by
supporting only what they need.
The program code (or hardware) that makes up
each layer has a defined responsibility. Each layer
also knows how to exchange information with the
layers directly above and below it, but a layer