Building the Web of Things with Sun SPOTs

Building the Web of Things with Sun SPOTs
Vipul Gupta and David G. Simmons, Sun Labs, Oracle
vipul.x.gupta@oracle.com, david.g.simmons@oracle.com

Ver: 20100921180500 JavaOne 2010, Hands-on Lab

Agenda

• Background: From the Internet of computers to the Internet of things.

• The Web of Things: Vision, relevant technologies, challenges in constrained
environments, examples.

• Introduction to Sun SPOTs: motivation, features.

• Lab overview and exercises:
• Sample “Flashlight” application on Sun SPOTs (Ex 1)
• RESTful web application on Sun SPOTs (Ex 2)
• Exposing the light sensor (Ex 3) and LEDs (Ex 4) as web resources
• Access control (Ex 5)

2

Background

• People have been connecting “things” to
the Internet even before the “Web”

More Info:
- Trojan room coffee pot
http://www.cl.cam.ac.uk/coffee/qsf/coffee.html
- Romkey & Hackett’s Internet Toaster, Interop ’90
http://www.savetz.com/yic/YIC11FI_6.html
- Robin Southgate, 2001
http://news.bbc.co.uk/2/hi/science/nature/1264205.stm

3

Background


• This trend is accelerating: phones,
household appliances, sensor platforms,
ambient devices, energy meters, health
and ﬁtness devices, asset tracking

4

Background



• Commercial entities are getting involved

• Lots of standards activities: IEEE, IETF,
IPSO, OGC, WWW

OAuth SensorML
Microformats 802.15.4
SWE
ROLL 6lowPAN CHTTP
EXI RHTTP Webhooks
CoRE

5

Background



• Commercial entities are getting involved

• Lots of standards activities: IEEE, IETF,
IPSO, OGC, WWW
“

• Recognition in mainstream media ’’
6

Background

• People have been connecting “things” to 10 fool-proof predictions for the Internet in 2020
3. The Internet will be a network of things,
not computers.
• This trend is accelerating: phones, As more critical infrastructure gets hooked up
household appliances, sensor platforms, to the Internet, the Internet is expected to
ambient devices, energy meters, health become a network of devices rather than a
and ﬁtness devices, asset tracking network of computers.Today, the Internet has
around 575 million host computers, according
to the CIA World Factbook 2009. But the NSF
• Commercial entities are getting involved is expecting billions of sensors on buildings
and bridges to be connected to the Internet for
such uses as electricity and security
• Lots of standards activities: IEEE, IETF, monitoring. By 2020, it's expected that the
IPSO, OGC, WWW number of Internet-connected sensors will be
orders of magnitude larger than the number of
users.
• Recognition in mainstream media

7

Motivation

• Comfort and entertainment -- smart environments (buildings, homes)

• Proactive health management -- both people and things (maintenance/repair)

• Better efﬁciency -- resource management (lower cost of heating/cooling)

• Timely access to information -- smart phones, environmental sensors

• Improved security and peace of mind -- accurate, responsive tracking of
valuable assets

Connected, smarter living

8

Commercial Opportunities

• “Things” or platforms for building “things”:
(Arduino, BugLabs, Sun SPOT, TED, Chumby, Nabztag, Nike
+iPod, Wattson, sensaware, Crossbow)

• Applications (PowerMeter, RunKeeper)

• Infrastructure components: gateways,
relay services
(therecorporation.com, iobridge.com, yaler.org)

• Platforms: middle-ware or hosted
service for data collection and
analysis
(Pachube, Sensor.Network)

9

Agenda





10

Web Of Things

• What?

“A vision where everyday devices and objects are integrated into the Web
using well-known standards and blueprints (URIs, HTTP, REST).”

“Seamless integration of physical and conceptual resources”

Also: “The physical web”, “the tactile web”

• How?
- Connect device to Internet,
- Embed web server,
- Model resources as URIs

11

REST (Representational State Transfer)

• Architectural style of the World Wide Web

• "The main idea of REST is to design applications which implement their
functionality completely as a set of URI-addressable resources,
with HTTP being the [uniform] access method for interacting with them.
In such an application, there is no need for any special interface, the
application fully blends into the Web ..."
-- Erik Wilde, UC Berkeley
Putting things to REST

More Info:
- Roy Fielding’s Ph.D. Thesis
(http://www.ics.uci.edu/~ﬁelding/pubs/dissertation/top.htm)
- REST Wiki (http://rest.blueoxen.net/)

12

REST in a Nutshell

• Identify application “resources” using URIs.

• Each resource implements some subset of a uniform interface:
POST (Create), GET (Read), PUT (Update), DELETE (Destroy).
Response codes describe method success/failure.

• Representations (XHTML, XML, JSON), conceptually separate from
resources, transferred in requests/responses.

• Representation includes metadata and links to related resources.

13

REST Examples

• Create a new resource, e.g. deploy an application

POST /apps HTTP/1.1
Content-Type: application/binary
Client Content-Length: 8914
Sun SPOT
<application binary>

HTTP/1.1 201 Created
Location: /apps/SensorSampler

• Delete a resource, e.g. undeploy an application

Client DELETE /apps/SensorSampler HTTP/1.1
Sun SPOT

HTTP/1.1 200 OK

14

REST Examples (cont’d)

• Read a resource, e.g. read the light sensor reading

GET /light HTTP/1.1
Client Accept: */*
Sun SPOT
HTTP/1.1 200 OK
Content-Type: text/plain
Content-Length: 3
138

• Update a resource, e.g. change color of LED 4
PUT /leds/4 HTTP/1.1
Client
Content-Length: 7
Sun SPOT
0,255,0

HTTP/1.1 200 OK

15

REST Beneﬁts

• Simpliﬁes integration of resources into the Web, making them accessible as
part of a global information system.

• Ease building of apps on top of embedded devices, dynamic ad-hoc
composite apps involving real-world devices (physical mashups)

• “Uniform interface” enables interaction with all sorts of devices via readily
available software (browsers, cURL)

• “Layered system” supports intermediaries, great for addressing device/
network constraints

• Get lots of features for free: caching, linking, security, bookmarking,
searching, (HTTP utilized as an application protocol, not just transport).

16

Network Bandwidth Constraints

• HTTP, XML are verbose. TCP connection setup/teardown adds overhead.

• Use caching, compression via binary encoding, use UDP, e.g. Efﬁcient XML
Interchange (http://www.w3.org/XML/EXI/), HTTP header compression (IETF CoRE, draft-tolle-
core-ebhttp-00, draft-frank-6lowpan-chopan-00)

Sun SPOT
Uncompressed Compressed

Client
GET /spot-5317/temp HTTP/1.1
Accept: */* 13 bytes
Host: localhost:8080 0000 - 68 36 47 2f 74 65 6d 70-00 0e 00 00 00 h6G/temp.....
Content-Length: 0
User-Agent: curl/7.19.7 ... zlib/1.2.3

HTTP/1.1 200 OK 18 bytes
0000 - 48 36 40 11 b0 01 0a 00-3c 0e 00 05 00 38 39 2e H6@.....<....89.
Cache-Control: max-age=60
0010 - 31 35 15
Content-Length: 5
89.15

17

Network Topology Constraints

• Device could be behind ﬁrewall/NAT, might move
• Use relay, with “long-poll” and Reverse HTTP (draft-lentczner-rhttp-00)

Sun SPOT

Client relay.net POST /spot-5317 HTTP/1.1
Upgrade: PTTH/1.0
Connection: Upgrade
Host: relay.net

HTTP/1.1 101 Switching Protocols
Upgrade: PTTH/1.0
Connection: Upgrade
GET /spot-5317/light HTTP/1.1
Host: relay.net GET /spot-5317/light HTTP/1.1
HTTP/1.1 200 OK
HTTP/1.1 200 OK
Connection: close
Connection: close
Content-Length: 3
Content-Length: 3
216
216

18

Energy Constraints

• Devices sleep periodically to conserve battery
• Use sleep-proxy to queue requests, cache responses zz

z
Sleep
zz zz
proxy
Sun SPOT
Client
(sleep notiﬁcation)
GET /spots/01AB/temp HTTP/1.1
Cache-Control: max-age=60
HTTP/1.1 200 OK
Age: 22
Content-Length: 5
86.45
PUT /spots/01AB/leds/5 HTTP/1.1
Content-Length: 7
0,255,0 HTTP/1.1 202 Accepted
Retry-After: 45
Location: spots/01AB/requests/1cqfw

19

Discovery

• Finding/understanding what a “thing” provides, relationship to other things

• Bootstrapping: Well deﬁned location for metadata (/.well-known, RFC 5785)

• Typed links: Use the “rel” attribute in links to describe relationships
(draft-nottingham-http-link-header-10), e.g.
Link: </>; rel=“http://example.net/foo’’

• Microformats (microformats.org)
<div class="vcard">
<div class="fn">Joe Doe</div>
<div class="org">The Example Company</div>
<div class="tel">604-555-1234</div>
<a class="url" href="http://example.com/">
http://example.com/</a>
</div>

See also: http://hueniverse.com/2009/11/the-discovery-protocol-stack-redux 20

Notiﬁcations

• Webhooks: an HTTP callback in the form of a POST
Client postbin.org
Sun SPOT

HEAD /spots/01AB/light HTTP/1.1
HTTP/1.1 200 OK
Link: </spots/01AB/light/web-hooks>,
rel=”subscriptions”

POST /spots/01AB/light/web-hooks HTTP/1.1
Notiﬁcation-Type: UPDATED
http://postbin.org/1c5r2aq
HTTP/1.1 201 CREATED
Location: /spots/01AB/light/web-hooks/1234
Link: </spots/01AB/light>, rel=”resource”

POST /postbin.org/1c5r2aq HTTP/1.1
...

21

Agenda





22

Sun SPOT Device

• Basic device has three layers
• Battery
• Processor Board with Radio
• Sensor Board (application
speciﬁc)

• Processor Board alone acts
as a base-station

• User programs the device
entirely in Java using
standard Java tools

23

Sun SPOT Capabilities/Technologies

Embedded Development Platform
Extremely ﬂexible hardware and software package
Easy to program - Java top to bottom
Java Device Drivers
Connected - Wireless Communication
Mesh Networking
Over the Air Programming
Mobile
Built in Lithium Ion battery charged through USB
Aware and Active
Able to sense and affect surroundings Built to Inspire!
(search for “spaughts” on
Secure Flickr/YouTube)
Built-in high grade ECC public key cryptography,
user-friendly key management

24

Sun SPOT Developer’s kit

• Two Full Sun SPOTs with
eDemoSensor boards and
batteries

• One base-station Sun SPOT

• Software

• Squawk VM

• Java SDK

• Netbeans

• USB cable, mounting clips

• Both hardware and software is
open source

• www.sunspotworld.com

25

Agenda





26

Exercise 1: “Flashlight” Application

• Shows Sun SPOTs ability to sense and respond to its environment.
Application automatically turns on the LEDs when ambient light is low

• Shows how to access resources (sensors, LEDs, switches) on the Sun SPOT

• Shows how to build and deploy a simple application and monitor its output

• Uses NetBeans for illustration but SDK is IDE agnostic

27

Exercise 2-5: Web Applications on Sun SPOT

• Learn about tools for building RESTful services on SPOTs

• Each exercise builds on the previous one, i.e. solution for an exercise is
included in the code for the next exercise :-)

• Exercise 2: Experiment and interact with pre-deﬁned services -- /.well-known
(meta-information), /status (read-only), /props (read/update/delete)
/blink

• Exercise 3: Develop a service for accessing the light sensor on SPOTs

• Exercise 4: Develop a service for accessing and updating LED color on SPOTs

• Exercise 5: Add authentication to the update operation in Exericse 4

28

Web Applications on Sun SPOTs

• Web applications are developed in a manner very similar to servlets

• Applications are hosted in a “Nano” app server

WebApp1

WebApp2
...

/app1

/app2
• Small footprint (~40KB) web application
container

• Runs on SPOT and host MetaApp
/.well-known

• WebApplications register to handle parts NanoAppServer
of the URL subspace

RHTTPHandler
• Supports compressed HTTP and

UDP6Handler
TCP6Handler
UDPHandler
TCPHandler
multiple request channels

• Built-in “MetaApp” handles
/.well-known (RFC 5785)

29

HOL Setup

Gateway

HTTP HTTP/CHTTP

TCP TCP/UDP

IP IPv6
6LoWPAN
Ethernet/WiFi/... 802.15.4
cURL: see curl.haxx.se

30

HOL Setup

• Lab attendees program SPOTs (far right)

• Gateway acts as protocol translator, caching agent and sleep proxy

• “Dashboard” web page makes periodic accesses to

• /spots on gateway for available SPOTs

• and for each SPOT on that list, it accesses

• spot-xxxx/status, spot-xxxx/light, spot-xxxx/leds

• Retrieved information is displayed graphically using Protovis*

*See http://vis.stanford.edu/protovis 31

Dashboard

Id
Name
Battery status
Status panel
Last heard

Success ratio
Light panel
Light Readings
LED panel LED Setting

32

Here the four SPOTs (from L to R) have completed Exercise 2, 3, 4 and 5 respectively.

33

Here the four SPOTs (from L to R) have completed Exercise 2, 3, 4 and 5 respectively.

34

Agenda





35

Exercise 1:

“Flashlight” Application (20 mins)

36

Exercise 1: Flashlight Application (page 1 of 3)

package org.sunspotworld;

import com.sun.spot.resources.Resources;
import com.sun.spot.resources.transducers.ILightSensor;
import com.sun.spot.resources.transducers.ISwitch;
import com.sun.spot.resources.transducers.ISwitchListener;
import com.sun.spot.resources.transducers.ITriColorLEDArray;
import com.sun.spot.resources.transducers.LEDColor;
import com.sun.spot.resources.transducers.SwitchEvent;
import com.sun.spot.util.*;

import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

/**
* The manifest speciﬁes this class as MIDlet-1, which means the VM
* will call the startApp method of this class to start the application.
*/
public class Flashlight extends MIDlet {
private static int LOW_LIGHT_THRESHOLD = 60;
private static LEDColor currentColor = LEDColor.WHITE;
private static int currentColorIdx = 0;
private static LEDColor[] colorChoices = {
LEDColor.WHITE, LEDColor.GREEN, LEDColor.CYAN, LEDColor.YELLOW
};
private ILightSensor lightSensor = null;
private ITriColorLEDArray myLEDs = null;
private ISwitch sw = null;

37


protected void startApp() throws MIDletStateChangeException {
int lightVal = 0;

System.out.println("Flashlight application starting ...n" + ... +
"Switch 1. Press Switch 2 to change LED color.n");

// Get the lightsensor, the LED array and the switch as a resource ...
lightSensor = (ILightSensor) Resources.lookup(ILightSensor.class);
myLEDs = (ITriColorLEDArray) Resources.lookup(ITriColorLEDArray.class);
// The resource lookup API supports tags ... this gets us Switch 2.
sw = (ISwitch) Resources.lookup(ISwitch.class, "SW2");

if ((lightSensor == null) || (myLEDs == null) || (sw == null)) {
System.err.println("Could not obtain necessary resources");
notifyDestroyed();
}

// Deﬁne & bind an anonymous switchlistener to change color on switch press
sw.addISwitchListener(new ISwitchListener() {
public void switchPressed(SwitchEvent evt) {
currentColorIdx = (currentColorIdx + 1) % (colorChoices.length);
currentColor = colorChoices[currentColorIdx];
System.out.println("New color is " + currentColor);
}

public void switchReleased(SwitchEvent evt) { }
});

38


while (true) { // In a loop ...
try {
// Get light reading ...
lightVal = lightSensor.getValue();
System.out.println("Light value is " + lightVal);

if (lightVal < LOW_LIGHT_THRESHOLD) {
// turn on the LEDs if light is below predeﬁned threshold
for (int i = 0; i < myLEDs.size(); i++) {
myLEDs.getLED(i).setColor(currentColor);
myLEDs.getLED(i).setOn();
}
} else {
// otherwise, turn off the LEDs
for (int i = 0; i < myLEDs.size(); i++) {
myLEDs.getLED(i).setOff();
}
}
} catch (Exception e) {
System.err.println("Caught " + e);
e.printStackTrace();
}

Utils.sleep(500);
}
}

....
}

39

Exercise 1: Running the Flashlight Application

• To build, deploy and run this application, connect the SPOT via a USB cable
to your computer and do one of the following:

• In NetBeans, right click on the project name “Exercise1” and choose “Run”

• In a terminal window, type the following command
% ant compile deploy run

• Output is shown on next two slides ...

40


...
-run-spotclient-once:
[java] SPOT Client starting...
[java] [waiting for reset] ...
[java] [waiting for reset] ...
[java] (please reset SPOT 0014.4F01.0000.xxxx on port /dev/cu.usbmodem621)

...
[java] Sun SPOT bootloader (yellow-100910)
[java] SPOT serial number = 0014.4F01.0000.FF22
[java] Writing SPOT properties (349 bytes) to local SPOT on port /dev/cu.usbmodem621
[java] |============================================================| 100%
[java]
[java]
[java] Using target ﬁle name: spotsuite://Sun_Microsystems_Inc/Exercise1
[java] Relocating application suite to 0x10900000
[java] About to ﬂash from /Users/vgupta/Desktop/OldDesktop/Docs/JavaOne2010/S314730_Sun_SPOTs_Web_Of_Things/
Exercises/Exercise1/suite/image
[java] Writing imageapp4934778024996327784.bintemp (4140 bytes) to local SPOT on port /dev/cu.usbmodem621
[java] |====== | 12%
[java] |============ | 24%
....
[java] |========================================================= | 97%
[java] |============================================================| 100%
[java]
[java]

41


-run-spotclient-once:
[java] SPOT Client starting...
[java]

[java] ** VM stopped: exit code = 0 **
[java]
[java] Starting midlet 1 in spotsuite://Sun_Microsystems_Inc/Exercise1
[java] Flashlight application starting ...
[java] To turn on the LEDs, cover the light sensor on the Sun SPOT.
[java] The light sensor is the tiny white square just underneath
[java] Switch 1. Press Switch 2 to change LED color.
[java]
[java] Light value is 23
[java] Light value is 24

42

Agenda





43

Exercise 2:

RESTful Web Application on SPOTs (20 mins)

44

Exercise 2: Anatomy of a Web Application

public class Status extends WebApplication {
• Deﬁne its processRequest() ...

public HttpResponse processRequest(HttpRequest request)
throws IOException {
• (Optionally) deﬁne isAuthroized() HttpResponse response = new HttpResponse();
String respStr = null;
String name = Spot.getInstance().getPersistentProperties().getProperty
("spot.name");

if (request.getMethod().equalsIgnoreCase("GET")) {
respStr = " ... +
Spot.getInstance().getPowerController().
getBattery().getBatteryLevel() + ...;

response.setStatus(HttpResponse.SC_OK);
response.setHeader("Content-Type", "text/plain");
// Controls caching at gateway
response.setHeader("Cache-Control", "max-age=30");
response.setBody(respStr.getBytes());

return response;
} else {
response.setStatus(HttpResponse.SC_METHOD_NOT_ALLOWED);
response.setHeader("Allow", "GET");

return response;
}
}
}

45

Exercise 2: Anatomy of a Web Application

public class WoTServer extends MIDlet {
• Deﬁne its processRequest() protected void startApp() throws MIDletStateChangeException {

try {
NanoAppServer nas = new NanoAppServer();

• (Optionally) deﬁne isAuthroized() nas.registerApp("/status", new Status("n=Access statusnsh=s"));
nas.registerApp("/props", new PropertiesManager("n=Properties
managernsh=pnd=http://bit.ly/aa8iOZ"));

if (WoTConstants.SVC_CONNECTION_TYPE.equals("udp")) {
• Register application with app server, new UDP6Handler(WoTConstants.TCP_UDP_SVCPORT, nas).start();
specifying } else {
new TCP6Handler(WoTConstants.TCP_UDP_SVCPORT, nas).start();
}
...

• URL to handle } catch (IOException ex) {
ex.printStackTrace();
}
}

• properties, e.g. name, protected void pauseApp() {
}
description, short URL
protected void destroyApp(boolean unconditional) throws
MIDletStateChangeException {
}
}

46

Exercise 2: Sample Interactions

• Replace address:port with a.b.c.d:8888*, xxxx with last four hex-digits in your
SPOT’s Id (see the back of “ﬁn”).

• Explore available services on your SPOT by pointing
your browser at http://address:port/spot-xxxx/.well-known/r
URL Name
/props, /p Properties
/status, /s Status
/blink, /b Blink LEDs

}
Try accessing http://address:port/spot-xxxx/.well-known/r?sh=p
Last four hex-digits
(Hint: ‘sh’ denotes ‘short URL’) 30D1

• Click on service name for documentation. Clicking on service URL causes a
“GET” on that service, Use cURL for other HTTP operations -- PUT, POST,
DELETE

*If you are following the lab exercises outside of the JavaOne hands-on lab, you’ll need to run the gateway code in Exercise/Gateway-onDesktop and replace a.b.c.d:8888 with the
address and port printed by the gateway application. 47

Exercise 2: Sample Interactions (/.well-known)

• List available services:
% curl --request GET --dump-header “hdrs.txt” “http://address:port/spot-xxxx/.well-known/r”
<table>
<tr><th>URL</th><th>Name</th></tr>
<tr><td><a href="../props">/props</a>, <a href="../p">/p</a></td><td><a href="http://bit.ly/aa8iOZ">Properties</a></td></tr>
<tr><td><a href="../status">/status</a>, <a href="../s">/s</a></td><td><a href="http://bit.ly/8YtWQE">Status</a></td></tr>
<tr><td><a href="../blink">/blink</a>, <a href="../b">/b</a></td><td><a href="http://bit.ly/bPAzq1">Blink LEDs</a></td></tr>
</table>

% more “hdrs.txt”
HTTP/1.1 200 OK
content-type:text/html
connection:close
cache-control:max-age=60
content-length:424

What do you notice if you retry these two shell commands
again soon after their previous invocation?

48

Exercise 2: Sample Interactions (/props)

• Read system properties:
% curl --request GET “http://address:port/spot-xxxx/props”
{
"spot.diagnostics": "true",
"spot.powercontroller.ﬁrmware.version": "PCTRL-1.105",
...
"spot.sdk.version": "yellow-100910",
"spot.hardware.rev": "6",
}

• Create a new system property:

% curl --request POST --data “spot.name: Louie” “http://address:port/spot-xxxx/props”
{
"spot.diagnostics": "true",
"spot.powercontroller.ﬁrmware.version": "PCTRL-1.105",
...
"spot.name": "Louie",
...
"spot.sdk.version": "yellow-100910",
"spot.hardware.rev": "6",
}

49

Exercise 2: Sample Interactions (/status)

• Read status (name, battery level, charging, uptime, endnode):
% curl --request GET “http://address:port/spot-xxxx/status”
{
n:"Louie",
b:36,
c:"n",
u:2169473,
e:"y"
}

• Other operations:
% curl --request POST “http://address:port/spot-xxxx/status” or

% curl --request PUT “http://address:port/spot-xxxx/status” or

% curl --request DELETE “http://address:port/spot-xxxx/status”

Client Error: 405 Method Not Allowed

50

Exercise 2: Sample Interactions (/blink)

• Read operation:
% curl --request GET --dump-header “hdrs.txt” “http://address:port/spot-xxxx/blink”

% more hdrs.txt
HTTP/1.1 405 Method Not Allowed
content-type:text/plain
connection:close
age:39
allow:POST
content-length:36

• Try POST:
% curl --request POST --data “255,255,0” “http://address:port/spot-xxxx/blink”
Successful: 200 OK

causes SPOT to blink its LEDs yellow.

51

Agenda





52

Exercise 3:

Light Sensor as a Web Resource (10 mins)

53

Exercise 3: Light sensor as a Web resource

• Create a simple web application (as described at http://bit.ly/aLqyNA) that
responds to HTTP GETs on /light by returning the light sensor reading
(Hint: See Exercise 1 for example code to retrieve light sensor reading.)

• Modiﬁcations required (look for lines starting XXX)

• HOLLightSensor.java: In processRequest(), modify respStr to return light sensor
reading (Hint: See Exercise 1 for example code)

• WoTServer.java: In startApp(), add another call to nas.registerApp registering the
light service implemented by HOLLightSensor (Hint: See code for pre-existing
services -- blink, status, props)

• If successful, dashboard page will automatically retrieve and display light
readings

54

Sample Interaction (/light)
% curl --request GET “http://address:port/spot-xxxx/light” --dump-header “hdrs.txt”
49

% cat hdrs.txt
HTTP/1.1 200 OK
connection:close
content-length:2

% curl --request GET “http://address:port/spot-xxxx/light” --dump-header “hdrs.txt”
49

% cat hdrs.txt
HTTP/1.1 200 OK
connection:close
age:5
content-length:2

% curl --request DELETE “http://address:port/spot-xxxx/light”

55

Agenda





56

Exercise 4:

LEDs as a Web Resource (15 mins)

57

Exercise 4: LEDs as a Web resource

• Create a simple web application (as described at http://bit.ly/9C3rlP) that
• responds to HTTP GETs on /leds by returning the LED color setting
• responds to HTTP PUTs on /leds by changing the LED color setting

(Hint: See Exercise 1 for sample code to access the LED resource)


• HOLLEDController.java: In processRequest(), modify respStr to show LED setting
in response to “GET” and ﬁll out handling of “PUT” requests.

• WoTServer.java: Add another call to nas.registerApp registering the LED service
implemented by HOLLEDController (Hint: See code for pre-existing services)

• If successful, dashboard page will automatically retrieve and display LED
setting (LED settings can also be changed by pressing Switch 2)

58

Sample Interaction (/leds)

% curl --request GET “http://address:port/spot-xxxx/leds”
[255,0,0]

% curl --request PUT --data “[255,255,0]” “http://address:port/spot-xxxx/leds”
Successful: 200 OK

% curl --request GET “http://address:port/spot-xxxx/leds”
[255,255,0]

% curl --request POST --data “[255,255,0]” “http://address:port/spot-xxxx/leds” --dump-header
“hdrs.txt

% more hdrs.txt
HTTP/1.1 405 Method Not Allowed
connection:close
allow:GET, PUT
content-length:36

59

Agenda





60

Exercise 5:

Adding Authentication (10 mins)

61

Exercise 5: Adding Authentication

• Add Basic HTTP Authentication so LED color changes require a password


• HOLLEDController.java:
In isAuthorized(), look for and match authorization header against expected value
for PUT requests. GET requests should be allowed without authorization checks.

• WoTServer.java:
Replace xxxx with last four hex-digits of your SPOT Id in the “realm” speciﬁcation.

62

Exercise 5: Adding Authentication
/*
* We only support HTTP Basic authentication which
* sends a Base-64 encoding of "username:password" in the
* "Authorization" header.
*
* General form:
* Authorization: <authType> <authToken>
*
* Example:
* Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
* ...
*/
public boolean isAuthorized(HttpRequest req) {
/* XXX Uncomment the following lines to authenticate PUTs. Replace "Ali Baba" with
* the authorized username and "open sesame" with the authorized password. */
// String authorizedUser = "Ali Baba";
// String authorizedPassword = "open sesame";
//
// if (req.getMethod().equalsIgnoreCase("PUT")) {
// String auth = req.getHeader("Authorization");
//
// return ((auth != null) && auth.equalsIgnoreCase("Basic " +
// Base64.encode(authorizedUser + ":" + authorizedPassword)));
// }

return true; // GETs should still succeed
}

63

Sample Interaction w/ Authentication Enabled

% curl --request PUT --data “[0,255,255]” “http://address:port/spot-xxxx/leds”
Client Error: 401 Unauthorized

% more hdrs.txt
HTTP/1.1 401 Unauthorized
connection:close
www-authenticate:Basic realm="spot-xxxx"
content-length:30

% curl --request PUT --data “[0,255,255]” --user "Ali Baba:open sesame" --basic
“http://address:port/spot-xxxx/leds”
Successful: 200 OK

% curl --request GET “http://address:port/spot-xxxx/leds” // GET needs no auth
[0,255,255]

64

Conclusion

• The Internet is rapidly becoming the “Internet of Things”

• Reusing/adapting well known concepts and technologies makes it easy to
incorporate everyday objects into the Web seamlessly

• Constrained devices like Sun SPOTs may require the introduction of a
gateway

• Emerging technologies (e.g. HTML 5, Webhooks) and phenomenon (e.g.
M2M, social networking) present interesting new opportunities

Download the Sun SPOT SDK from http://www.sunspotworld.com/ and experiment with the
bundled “WebOfThings” demo, e.g. try RHTTP

65

Thank You! (and send us your feedback)

This lab would not have been possible without the work of Sun SPOT team
members, both past and present.

Sun SPOT team members ﬂanked by Sun executives Greg P and Jonathan Schwartz (from L to R): Pete St. Pierre, Derek White, Roger
Meike, Randy Smith, David G. Simmons, Ron Goldman, Arshan Poursohi, Eric Arseneau,Vipul Gupta, Bob Alkire, Poorna Udupi (not shown)

66

Building the Web of Things with Sun SPOTs

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