CoAP request-response model in IOT Protocols - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the CoAP method for a GET request.

IOT Protocols

coap_request.method = '[1]'

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

APUT

BGET

CPOST

DDELETE

Attempts:

3 left

💡 Hint

Common Mistakes

Using POST instead of GET for retrieving data.

The GET method is used to retrieve data in the CoAP request-response model.

2fill in blank

medium

Complete the code to set the CoAP response code for a successful content response.

IOT Protocols

coap_response.code = '[1]'

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

A2.05 Content

B4.04 Not Found

C5.00 Internal Server Error

D2.01 Created

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing error codes like 4.04 or 5.00 for successful responses.

The response code 2.05 Content indicates a successful response with the requested content.

3fill in blank

hard

Fix the error in the CoAP message type assignment for a confirmable message.

IOT Protocols

coap_message.type = '[1]'

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

ARST

BACK

CNON

DCON

Attempts:

3 left

💡 Hint

Common Mistakes

Using NON (non-confirmable) instead of CON for confirmable messages.

CON stands for Confirmable message type in CoAP, which requires acknowledgment.

4fill in blank

hard

Fill both blanks to create a CoAP request with method POST and message type NON.

IOT Protocols

coap_request.method = '[1]'
coap_request.type = '[2]'

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

APOST

BGET

CNON

DCON

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing message types or using GET instead of POST for sending data.

POST is used to send data, and NON is a non-confirmable message type that does not require acknowledgment.

5fill in blank

hard

Fill all three blanks to define a CoAP response with code 2.01 Created, type ACK, and method PUT.

IOT Protocols

coap_response.code = '[1]'
coap_response.type = '[2]'
coap_request.method = '[3]'

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

A2.01 Created

BACK

CPUT

DCON

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing message types or response codes for resource creation.

2.01 Created indicates resource creation success, ACK is acknowledgment message type, and PUT is used to update or create resources.

Practice

1. What is the main purpose of the CoAP request-response model?

easy

A. To create user interfaces for IoT devices

B. To store data permanently on a server

C. To send a request and receive a response between devices

D. To encrypt messages between devices

Solution

1. Step 1: Understand CoAP communication basics

   CoAP is designed to allow devices to send requests and get responses, similar to asking a question and getting an answer.

2. Step 2: Identify the purpose of request-response

   The request-response model is about communication, not storage, encryption, or UI creation.

3. Final Answer:

   To send a request and receive a response between devices -> Option C

4. Quick Check:

   Request-response = send and receive [OK]

Hint: Request-response means ask and answer communication [OK]

Common Mistakes:

• Confusing request-response with data storage
• Thinking CoAP handles encryption by default
• Assuming CoAP creates user interfaces

2. Which CoAP method is used to retrieve data from a device?

easy

A. GET

B. POST

C. DELETE

D. PUT

Solution

1. Step 1: Recall CoAP methods

   CoAP uses methods similar to HTTP: GET, POST, PUT, DELETE.

2. Step 2: Identify method for retrieving data

   GET is used to request and retrieve data from a device.

3. Final Answer:

   GET -> Option A

4. Quick Check:

   GET = retrieve data [OK]

Hint: GET method always fetches data [OK]

Common Mistakes:

• Using POST to retrieve data instead of send
• Confusing PUT with GET
• Thinking DELETE retrieves data

3. Given a CoAP GET request to a sensor, what is the expected response code if the data is successfully retrieved?

medium

A. 2.05 Content

B. 4.04 Not Found

C. 5.00 Internal Server Error

D. 3.01 Moved Permanently

Solution

1. Step 1: Understand CoAP response codes

   CoAP uses numeric codes similar to HTTP. 2.xx codes mean success, 4.xx client error, 5.xx server error.

2. Step 2: Identify success code for GET response

   2.05 Content means the request succeeded and the content is returned.

3. Final Answer:

   2.05 Content -> Option A

4. Quick Check:

   Success code for GET = 2.05 Content [OK]

Hint: 2.xx codes mean success in CoAP [OK]

Common Mistakes:

• Choosing 4.04 which means resource not found
• Confusing 5.00 server error with success
• Thinking 3.01 means success instead of redirect

4. A CoAP client sends a POST request but receives no response. What is the most likely cause?

medium

A. The server does not support POST method

B. The request was sent as non-confirmable and got lost

C. The client used an invalid URI format

D. The server returned a 2.05 Content response

Solution

1. Step 1: Understand CoAP message types

   CoAP supports confirmable (CON) and non-confirmable (NON) messages. NON messages may be lost without retry.

2. Step 2: Analyze no response scenario

   If a POST is sent as NON and network drops it, no response is received.

3. Final Answer:

   The request was sent as non-confirmable and got lost -> Option B

4. Quick Check:

   NON messages can be lost without response [OK]

Hint: Non-confirmable messages may get lost silently [OK]

Common Mistakes:

• Assuming server always supports POST
• Confusing invalid URI with no response
• Thinking 2.05 Content means no response

5. You want to update a device's configuration using CoAP. Which method should you use and what response code indicates success?

hard

A. DELETE method with 2.02 Deleted response

B. POST method with 4.00 Bad Request response

C. GET method with 2.05 Content response

D. PUT method with 2.04 Changed response

Solution

1. Step 1: Identify method for updating data

   PUT is used to update or replace a resource on the device.

2. Step 2: Find success response code for update

   2.04 Changed means the update was successful.

3. Final Answer:

   PUT method with 2.04 Changed response -> Option D

4. Quick Check:

   Update = PUT + 2.04 Changed [OK]

Hint: PUT updates; 2.04 means update success [OK]

Common Mistakes:

• Using GET to update data
• Confusing 4.00 error as success
• Mixing DELETE with update operation