Virtual Labs

Simulation of sending live sensors data on IoT Platform using MQTT Protocols and ESP8266/ESP32

1. Compare publish–subscribe and client–server models. Which statement is correct?

a: Client–server allows many clients to send messages without a server Explanation

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b: Publish–subscribe requires direct connection between publisher and subscriber Explanation

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c: Publish–subscribe uses a broker to route messages between publishers and subscribers Explanation

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d: Client–server is event-driven like publish–subscribe Explanation

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2. Why is MQTT preferred in battery-powered IoT devices?

a: It consumes more power than HTTP Explanation

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b: It requires high bandwidth Explanation

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c: It is lightweight and uses low power Explanation

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d: It does not support sleep modes Explanation

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3. How does QoS improve message delivery in MQTT?

a: By increasing Wi-Fi speed Explanation

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b: By controlling how reliably messages are delivered Explanation

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c: By reducing broker memory usage Explanation

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d: By encrypting all messages automatically Explanation

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4. How do MQTT topics work?

a: They store sensor data permanently Explanation

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b: They define channels where messages are published and subscribed Explanation

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c: They are used only for authentication Explanation

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d: They control Wi-Fi connection strength Explanation

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5. What happens when ESP8266 loses internet connection during MQTT publish?

a: Message is always delivered later automatically Explanation

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b: Publish fails and may be retried depending on QoS Explanation

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c: Broker sends the data using SMS Explanation

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d: ESP8266 switches to HTTP mode Explanation

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6. Which is an example use case of MQTT in smart homes?

a: Sending emails from a computer Explanation

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b: Controlling lights and switches using publish–subscribe messages Explanation

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c: Running heavy data analytics Explanation

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d: Offline data storage Explanation

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7. What is the difference between MQTT broker and subscriber?

a: Broker publishes sensor data; subscriber receives it Explanation

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b: Subscriber stores all messages permanently Explanation

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c: Broker routes messages; subscriber receives messages from topics Explanation

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d: Subscriber connects devices to the internet Explanation

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8. How can multiple sensors send data using a single MQTT topic?

a: By using UDP packets Explanation

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b: By sending data through different brokers Explanation

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c: By publishing structured or labeled data to the same topic Explanation

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d: By enabling Bluetooth mode Explanation

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9. Why is MQTT considered lightweight?

a: It uses complex headers Explanation

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b: It requires large memory Explanation

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c: It uses very small packet sizes and minimal overhead Explanation

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d: It needs constant high-speed internet Explanation

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10. How can dashboards like Node-RED or MQTT Explorer visualize MQTT data?

a: By blocking broker connections Explanation

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b: By connecting as subscribers and displaying incoming messages Explanation

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c: By converting MQTT into SMS alerts Explanation

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d: By sending data directly to Arduino pins Explanation

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