A short presentation of how to turn an Arduino (open source physical computing platform) into a web server in around 20 lines of code.

1. Creating an Arduino Web
Server
From scratch hardware and software

2. Web Servers
Simpler than you think
A web server
Listens for connections
Parses requests
Send back status messages and resource
requested

3. Arduino Overview
Open source physical computing platform
Multiple form factors
Easy to code (C/C++ like) and use (USB)
Low cost
Great for prototypes, wearable computers,
sensor networks etc

4. Arduino Hardware
ATMega 8 bit microcontroller
32K program memory, 2K SRAM, 1K EEPROM
Dual purpose digital inputs and outputs
Analog inputs
High performance (16 MIPS)
Low power (3.3V or 5V)

5. Arduino IDE/Software
Open source
Cross platform (Mac, PC and Linux)
Alpha but stable
Simple to use
Includes documentation, help, samples and
library for common tasks

6. Arduino Shields
Hardware can be easily extended
Shields plug in on top of standard boards
Build your own or buy off the shelf (lots
available)
Stackable, can use more than one

7. Ethernet Shields
Several shields available
Two main types DHCP and non DHCP
Some configuration required
Non DHCP you set IP and MAC address in
code

8. IP and MAC address
Set IP address and MAC address in your
code
Need to be careful with duplicates
Set up like so:
Ethernet.begin(mac, ip);

9. Ethernet Library
Standard ethernet library
Includes Client and Server classes
Create server like so:
Server server(80);
server.begin();
Bare bones web server about 20 lines of
code and 5K compiled

10. HTTP Protocol
HyperText Transfer Protocol
Used by web servers to transfer web pages
to be displayed in your web browser
Connection (usually) on port 80

11. TCP Connections
TCP three way connection handshake
Client sends SYN with random number (A)
Server replies with SYN-ACK containing A+1
and random number (B)
Client replies with ACK containing B+1
Luckily ethernet library does this for you!

12. Connection Code
Create a client
Client client = server.available();
Connected
while (client.connected()
{
....
}

13. HTTP Requests
Start with request “GET index.html HTTP/1.1”
Optional headers “Accept-Language: en”
Empty line
Optional message body (POST and other
requests)

14. HTTP Request Hack
Standard GET request have request followed
by blank line
So just ignore what is requested and check
for blank line

15. Request Code
Read characters
char c = client.read();
If newline and last character was newline
if (c == 'n' && blankline) {
...
}
if (c == 'n') {
blankline = true;
}

16. HTTP Response
Send back status line "HTTP/1.1 200 OK"
Send back content type "Content-Type: text/
html"
Send blank line
Send (HTML) content

17. Response Code
Send status and content type
client.println("HTTP/1.1 200 OK");
client.println("Content-Type: text/html");
client.println();
Send content
for (int i =0; i < nolines; i++) {
client.println(content[i]);
}

18. Close Connections
Clear up after you
client.flush();
client.stop();

19. Arduiono Web Server
Demo
Aruino IDE
Web browser