HTTP request methods for IoT (GET, POST, PUT) in IOT Protocols - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding HTTP GET method in IoT

Which statement best describes the purpose of the HTTP GET method when used in IoT devices?

A It deletes a resource from the server.

B It requests data from a server without changing any resource on the server.

C It updates an existing resource on the server with new data.

D It sends new data to the server to create a resource.

💡 Hint

Think about when you want to read sensor data without changing anything.

The GET method is used to retrieve data from a server. It does not modify any data or resource on the server, making it safe and idempotent.

💻 Command Output

intermediate

Output of HTTP POST request in IoT

What is the typical server response status code after a successful HTTP POST request from an IoT device sending new sensor data?

A 201 Created

B 404 Not Found

C 204 No Content

D 200 OK

💡 Hint

Consider what status code means a new resource was successfully created.

HTTP 201 Created indicates that the server has successfully created a new resource as a result of the POST request.

❓ Configuration

advanced

Configuring HTTP PUT for IoT device firmware update

You want to update the firmware on an IoT device using HTTP PUT. Which of the following best describes the correct use of PUT in this context?

A PUT requests the current firmware version without changing it.

B PUT sends partial data to update only some fields of the firmware metadata.

C PUT deletes the existing firmware before uploading new firmware.

D PUT replaces the entire firmware resource on the device with the new firmware data.

💡 Hint

Think about how PUT differs from PATCH in updating resources.

PUT replaces the entire resource at the target URL. For firmware updates, this means the whole firmware is replaced with the new version.

❓ Troubleshoot

advanced

Troubleshooting HTTP POST failure in IoT sensor data upload

An IoT device tries to send sensor data using HTTP POST but receives a 405 Method Not Allowed error. What is the most likely cause?

A The server does not support POST method at the requested URL.

B The device sent data using GET instead of POST.

C The server is down and cannot process any requests.

D The device's network connection is lost.

💡 Hint

405 means the method is not allowed on the server for that URL.

A 405 error means the server understands the request method but refuses to allow it for the target resource, often because POST is not enabled there.

🔀 Workflow

expert

Choosing HTTP methods for IoT device data lifecycle

Arrange the HTTP methods in the correct order to represent a typical IoT device data lifecycle: retrieving current data, sending new data, and updating existing data.

A 1,3,2

B 2,1,3

C 1,2,3

D 3,2,1

💡 Hint

Think about the natural flow: first read, then create, then update.

The typical flow is GET to retrieve data, POST to send new data, and PUT to update existing data.

Practice

1. Which HTTP method is used to retrieve data from an IoT device without changing it?

easy

A. POST

B. DELETE

C. PUT

D. GET

Solution

1. Step 1: Understand the purpose of GET

   GET is designed to fetch or read data without modifying it on the server or device.

2. Step 2: Compare with other methods

   POST sends new data, PUT updates existing data, DELETE removes data. Only GET fetches without change.

3. Final Answer:

   GET -> Option D

4. Quick Check:

   GET = fetch data without change [OK]

Hint: GET fetches data, POST sends new, PUT updates existing [OK]

Common Mistakes:

• Confusing POST with GET as both send data
• Thinking PUT fetches data
• Using DELETE instead of GET for retrieval

2. Which of the following is the correct syntax to send data using POST method in an HTTP request for IoT?

easy

A. PUT /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22}

B. POST /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22}

C. GET /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22}

D. DELETE /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22}

Solution

1. Step 1: Identify the method for sending new data

   POST is used to send new data to the server or device, so the request line must start with POST.

2. Step 2: Check the syntax correctness

   The syntax includes the method, path, HTTP version, headers, and body. POST /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22} correctly uses POST with JSON data.

3. Final Answer:

   POST /device/data HTTP/1.1\nContent-Type: application/json\n\n{"temp": 22} -> Option B

4. Quick Check:

   POST sends data with correct syntax [OK]

Hint: POST method starts the request line to send data [OK]

Common Mistakes:

• Using GET method to send data
• Missing Content-Type header
• Using DELETE or PUT instead of POST for new data

3. Given this HTTP request to update a device setting:

PUT /device/settings HTTP/1.1\nContent-Type: application/json\n\n{"mode": "eco"}

What is the expected result on the device?

medium

A. The device mode is updated to 'eco'.

B. The device sends back current settings without change.

C. A new device setting is created without replacing existing ones.

D. The device deletes the current settings.

Solution

1. Step 1: Understand the PUT method purpose

   PUT replaces or updates existing data on the device with the provided data.

2. Step 2: Analyze the request body

   The JSON body sets "mode" to "eco", so the device's mode setting will be updated accordingly.

3. Final Answer:

   The device mode is updated to 'eco'. -> Option A

4. Quick Check:

   PUT updates existing data [OK]

Hint: PUT updates or replaces existing data on device [OK]

Common Mistakes:

• Thinking PUT only adds new data without replacing
• Confusing PUT with GET which fetches data
• Assuming DELETE is used to update data

4. You wrote this HTTP request to update sensor data:

POST /sensor/data HTTP/1.1\nContent-Type: application/json\n\n{"humidity": 45}

But the device does not update the data. What is the likely error?

medium

A. The JSON body is invalid.

B. Content-Type header is missing.

C. POST is incorrect; PUT should be used to update existing data.

D. GET method should be used instead of POST.

Solution

1. Step 1: Identify the purpose of the request

   The request aims to update existing sensor data, which requires the PUT method.

2. Step 2: Check the method used

   POST is for sending new data, not updating. Using POST here causes the device to ignore the update.

3. Final Answer:

   POST is incorrect; PUT should be used to update existing data. -> Option C

4. Quick Check:

   Use PUT to update data, not POST [OK]

Hint: Use PUT to update, POST to create new data [OK]

Common Mistakes:

• Using POST instead of PUT for updates
• Ignoring Content-Type header importance
• Confusing GET with POST for data changes

5. An IoT device API supports GET, POST, and PUT methods. You want to add a new temperature reading and then update the device's configuration mode. Which sequence of HTTP requests should you use?

hard

A. POST to add temperature, then PUT to update configuration

B. PUT to add temperature, then POST to update configuration

C. GET to add temperature, then PUT to update configuration

D. POST to add temperature, then POST to update configuration

Solution

1. Step 1: Identify method for adding new data

   POST is used to send new data, so adding a temperature reading requires POST.

2. Step 2: Identify method for updating existing data

   PUT updates or replaces existing data, so updating configuration mode requires PUT.

3. Step 3: Determine correct sequence

   First POST to add new reading, then PUT to update configuration.

4. Final Answer:

   POST to add temperature, then PUT to update configuration -> Option A

5. Quick Check:

   POST new data, PUT update existing [OK]

Hint: POST adds new, PUT updates existing; order matters [OK]

Common Mistakes:

• Using PUT to add new data
• Using POST to update existing data
• Using GET for data changes