JSON payload formatting in IOT Protocols - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this JSON payload after parsing?

Given this JSON payload received from an IoT sensor:

{"temperature": 22.5, "humidity": 48, "status": "ok"}

What will be the value of the status field after parsing?

A null

B "ok"

C ok

D "OK"

💡 Hint

Remember JSON strings are enclosed in double quotes and parsing keeps string values as strings.

The status field is a string with value "ok". After parsing, it remains a string with quotes in code representation.

❓ Configuration

intermediate

Which JSON payload is correctly formatted for sending sensor data?

You want to send temperature and humidity data from a sensor in JSON format. Which of these payloads is correctly formatted?

A {temperature: 25, humidity: 60}

B {"temperature": 25, "humidity": 60}

C {"temperature": "25", "humidity": 60}

D {"temperature": 25, humidity: 60}

💡 Hint

JSON keys must be in double quotes and values can be numbers or strings.

Option B uses double quotes for keys and numeric values correctly. Option B and D miss quotes on keys. Option B uses a string for temperature which is allowed but less ideal for numeric data.

❓ Troubleshoot

advanced

Why does this JSON payload cause a parsing error?

This JSON payload is sent from a device:

{"temp": 22.5, "humidity": 55, "status": ok}

Why does it cause a parsing error?

A The commas between fields are missing.

B The temperature value 22.5 must be an integer.

C The keys temp and humidity must be numbers, not strings.

D The value ok is not in double quotes, so it's invalid JSON.

💡 Hint

In JSON, string values must be enclosed in double quotes.

The value ok is a string but is not enclosed in double quotes, causing a JSON parsing error.

🔀 Workflow

advanced

What is the correct order to process an incoming JSON payload from an IoT device?

Arrange these steps in the correct order to handle a JSON payload from an IoT sensor:
1. Validate JSON format
2. Parse JSON into data structure
3. Send acknowledgment to device
4. Extract sensor values

A 1,2,4,3

B 2,1,4,3

C 1,4,2,3

D 4,1,2,3

💡 Hint

You must check format before parsing, then extract data, then respond.

First validate the JSON format to avoid errors, then parse it, extract needed values, and finally send acknowledgment.

✅ Best Practice

expert

Which JSON payload design is best for extensibility in IoT sensor data?

You want to design a JSON payload for sensor data that may add new fields later. Which design is best?

A {"sensor_id": "123", "data": {"temp": 22.5, "humidity": 55}}

B {"sensor_id": "123", "temp": 22.5, "humidity": 55}

C [{"sensor_id": "123"}, {"temp": 22.5}, {"humidity": 55}]

D {"123": {"temp": 22.5, "humidity": 55}}

💡 Hint

Grouping sensor data inside a nested object helps add new fields without changing the main structure.

Option A groups sensor readings inside a 'data' object, making it easier to add new sensor fields later without changing the top-level keys.

Practice

1. What is the main purpose of using JSON payloads in IoT communication?

easy

A. To organize data in a clear, readable way

B. To encrypt data for security

C. To compress data for faster transfer

D. To convert data into binary format

Solution

1. Step 1: Understand JSON payload role

   JSON payloads structure data using key-value pairs, making it easy to read and understand.

2. Step 2: Compare with other options

   Encryption, compression, and binary conversion are different processes not handled by JSON formatting.

3. Final Answer:

   To organize data in a clear, readable way -> Option A

4. Quick Check:

   JSON = clear data format [OK]

Hint: JSON is for clear data structure, not encryption or compression [OK]

Common Mistakes:

• Confusing JSON formatting with encryption
• Thinking JSON compresses data
• Assuming JSON converts data to binary

2. Which of the following is a correctly formatted JSON payload snippet?

easy

A. { 'temperature': 22, 'humidity': 60 }

B. { "temperature": 22, "humidity": 60 }

C. { temperature: 22, humidity: 60 }

D. { temperature = 22, humidity = 60 }

Solution

1. Step 1: Check JSON key formatting

   JSON keys must be in double quotes, so "temperature" and "humidity" are correct.

2. Step 2: Validate value syntax

   Values like 22 and 60 are valid numbers without quotes. Other options use invalid quotes or syntax.

3. Final Answer:

   { "temperature": 22, "humidity": 60 } -> Option B

4. Quick Check:

   Keys need double quotes in JSON [OK]

Hint: Keys in JSON always use double quotes " " [OK]

Common Mistakes:

• Using single quotes instead of double quotes
• Omitting quotes around keys
• Using equals sign instead of colon

3. Given this JSON payload:

{"device": "sensor1", "status": "active", "battery": 85}

What is the value of the battery key?

medium

A. 85

B. "85"

C. battery

D. null

Solution

1. Step 1: Locate the battery key in JSON

   The key "battery" has the value 85 without quotes, meaning it is a number.

2. Step 2: Understand JSON value types

   Numbers in JSON are written without quotes, so the value is the number 85, not a string.

3. Final Answer:

   85 -> Option A

4. Quick Check:

   Number values have no quotes in JSON [OK]

Hint: Numbers in JSON have no quotes, strings do [OK]

Common Mistakes:

• Confusing numbers with strings by adding quotes
• Selecting the key name instead of its value
• Assuming missing keys return null

4. Identify the error in this JSON payload:

{"temp": 25, "humidity": 55,}

medium

A. Missing quotes around keys

B. Keys and values swapped

C. Using single quotes instead of double quotes

D. Trailing comma after last item

Solution

1. Step 1: Check JSON syntax for commas

   JSON does not allow a comma after the last key-value pair, so the comma after 55 is invalid.

2. Step 2: Verify other syntax elements

   Keys have double quotes, and values are correct. No other syntax errors present.

3. Final Answer:

   Trailing comma after last item -> Option D

4. Quick Check:

   No trailing commas allowed in JSON [OK]

Hint: No comma after last item in JSON objects [OK]

Common Mistakes:

• Leaving trailing commas after last pair
• Forgetting quotes around keys
• Mixing single and double quotes

5. You want to send a JSON payload from an IoT device reporting temperature and status. Which of these payloads correctly formats a nested JSON object for location with latitude and longitude?

hard

A. { "temperature": 20, "status": "ok", "location": ( "lat": 40.7128, "lon": -74.0060 ) }

B. { "temperature": 20, "status": "ok", "location": [ "lat": 40.7128, "lon": -74.0060 ] }

C. { "temperature": 20, "status": "ok", "location": { "lat": 40.7128, "lon": -74.0060 } }

D. { "temperature": 20, "status": "ok", "location": "lat": 40.7128, "lon": -74.0060 }

Solution

1. Step 1: Understand nested JSON objects

   Nested objects use curly braces { } with key-value pairs inside, so location must be an object with lat and lon keys.

2. Step 2: Check each option's structure

   { "temperature": 20, "status": "ok", "location": { "lat": 40.7128, "lon": -74.0060 } } uses curly braces correctly. { "temperature": 20, "status": "ok", "location": [ "lat": 40.7128, "lon": -74.0060 ] } uses square brackets which are for arrays, not objects. { "temperature": 20, "status": "ok", "location": ( "lat": 40.7128, "lon": -74.0060 ) } uses parentheses which are invalid. { "temperature": 20, "status": "ok", "location": "lat": 40.7128, "lon": -74.0060 } has keys outside an object.

3. Final Answer:

   { "temperature": 20, "status": "ok", "location": { "lat": 40.7128, "lon": -74.0060 } } -> Option C

4. Quick Check:

   Nested objects use curly braces { } [OK]

Hint: Use { } for nested objects, [ ] for arrays in JSON [OK]

Common Mistakes:

• Using brackets [] instead of braces {} for objects
• Using parentheses () which are invalid in JSON
• Placing keys outside any object or array