Observe option for notifications in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable observation of a resource for notifications.

IOT Protocols

client.observe([1], onNotification);

Drag options to blanks, or click blank then click option'

AresourcePath

Bobserve

Cnotify

Dsubscribe

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names instead of resource path

Passing callback as first argument

The observe method requires the resource path to start observing notifications.

2fill in blank

medium

Complete the code to handle notifications when observing a resource.

IOT Protocols

function onNotification([1]) {
  console.log('Notification received:', data);
}

Drag options to blanks, or click blank then click option'

Adata

Bevent

Cmessage

Dnotification

Attempts:

3 left

💡 Hint

Common Mistakes

Using event instead of data

Not defining a parameter

The callback receives the notification data as the first argument, commonly named data.

3fill in blank

hard

Fix the error in the code to correctly start observing notifications.

IOT Protocols

client.[1]('sensor/temp', onNotification);

Drag options to blanks, or click blank then click option'

Asubscribe

Bnotify

Cobserve

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using notify instead of observe

Using subscribe which is not supported

The correct method to start observation is observe. Other methods like notify or subscribe are incorrect here.

4fill in blank

hard

Fill both blanks to create an observe request with options for notifications.

IOT Protocols

client.observe('[1]', { [2]: true }, onNotification);

Drag options to blanks, or click blank then click option'

Asensor/humidity

Bconfirmable

CnonConfirmable

Dsensor/pressure

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong resource path

Using nonConfirmable instead of confirmable

The resource path is 'sensor/humidity' and the option to make notifications confirmable is 'confirmable: true'.

5fill in blank

hard

Fill all three blanks to correctly observe a resource with options and handle notifications.

IOT Protocols

client.observe('[1]', { [2]: true, [3]: 30 }, onNotification);

Drag options to blanks, or click blank then click option'

Asensor/light

Bconfirmable

CmaxAge

Dtimeout

Attempts:

3 left

💡 Hint

Common Mistakes

Using timeout instead of maxAge

Wrong resource path

Missing confirmable option

The resource is 'sensor/light', the notifications are confirmable, and maxAge sets the max age of cached data.

Practice

1. What is the main purpose of the Observe option in IoT protocols like CoAP?

easy

A. To allow clients to receive automatic updates from the server without repeated requests

B. To encrypt the data sent between client and server

C. To authenticate the client before data transfer

D. To compress the data for faster transmission

Solution

1. Step 1: Understand the Observe option function

   The Observe option enables clients to subscribe to resource changes and get updates automatically.

2. Step 2: Compare with other options

   Encryption, authentication, and compression are different features unrelated to Observe.

3. Final Answer:

   To allow clients to receive automatic updates from the server without repeated requests -> Option A

4. Quick Check:

   Observe = automatic updates [OK]

Hint: Observe means automatic updates without asking repeatedly [OK]

Common Mistakes:

• Confusing Observe with security features
• Thinking Observe compresses data
• Assuming Observe authenticates clients

2. Which of the following is the correct way to include the Observe option in a CoAP GET request?

easy

A. Add option number 14 with value 1 in the request header

B. Add option number 12 with value 1 in the request header

C. Add option number 14 with value 0 in the request header

D. Add option number 15 with value 0 in the request header

Solution

1. Step 1: Identify Observe option number and value

   Observe option in CoAP is option number 14. To register for notifications, value 0 is used.

2. Step 2: Match correct option number and value

   Option 14 with value 0 is the correct way to request observation.

3. Final Answer:

   Add option number 14 with value 0 in the request header -> Option C

4. Quick Check:

   Observe option = 14, value = 0 [OK]

Hint: Observe option number is 14, value 0 to observe [OK]

Common Mistakes:

• Using wrong option number
• Using wrong value for Observe
• Confusing Observe option with other options

3. Given this CoAP client code snippet requesting observation:

GET /sensor/temp
Options: Observe=0

What will the client receive after the initial response?

medium

A. Only the initial temperature value, no updates

B. Initial value plus automatic updates when temperature changes

C. An error because Observe=0 is invalid

D. Only updates without initial value

Solution

1. Step 1: Understand Observe=0 meaning

   Observe=0 means the client wants to register for notifications and receive updates.

2. Step 2: Expected server behavior

   The server sends the initial resource value, then sends notifications when the value changes.

3. Final Answer:

   Initial value plus automatic updates when temperature changes -> Option B

4. Quick Check:

   Observe=0 means subscribe and get updates [OK]

Hint: Observe=0 means subscribe and get updates including initial [OK]

Common Mistakes:

• Thinking Observe=0 disables updates
• Expecting error from Observe=0
• Assuming updates come without initial value

4. A client sends a CoAP GET request with Observe=2 option. The server does not send notifications. What is the likely problem?

medium

A. Client forgot to include URI path

B. Server does not support Observe option

C. Server requires Observe=3 to send notifications

D. Observe=2 is invalid; client must use 0 or 1 to register

Solution

1. Step 1: Check valid Observe values

   Valid Observe values for registration are 0 or 1. Value 2 is not defined for Observe.

2. Step 2: Understand server behavior

   Server ignores invalid Observe values and does not send notifications.

3. Final Answer:

   Observe=2 is invalid; client must use 0 or 1 to register -> Option D

4. Quick Check:

   Observe values must be 0 or 1 [OK]

Hint: Observe option values are only 0 or 1 for notifications [OK]

Common Mistakes:

• Using unsupported Observe values
• Assuming server requires special values
• Ignoring invalid option values

5. You want to monitor a sensor's state changes efficiently using CoAP Observe. Which approach best saves battery and network usage?

hard

A. Use Observe option to get notifications only when sensor state changes

B. Send repeated GET requests every second without Observe

C. Use Observe option but ignore notifications and poll manually

D. Send a single GET request and never update

Solution

1. Step 1: Understand Observe benefits

   Observe lets the client receive updates only when the sensor state changes, avoiding repeated requests.

2. Step 2: Compare with other methods

   Repeated GET requests waste battery and network. Ignoring notifications defeats Observe purpose. Single request never updates.

3. Final Answer:

   Use Observe option to get notifications only when sensor state changes -> Option A

4. Quick Check:

   Observe saves battery by sending updates only on changes [OK]

Hint: Observe sends updates only on changes, saving resources [OK]

Common Mistakes:

• Polling too frequently wasting battery
• Ignoring Observe notifications
• Not using Observe for real-time updates