Raspberry Pi - MQTT for IoT
Which QoS level ensures that a message is received exactly once by the subscriber?
Which QoS level ensures that a message is received exactly once by the subscriber?
easy🧠 Conceptual Q2 of 15
Step-by-Step Solution
Solution:
Step 1: Recall QoS levels in MQTT
QoS 0 is at most once, QoS 1 is at least once, QoS 2 is exactly once.Step 2: Identify the level for exactly once delivery
QoS 2 uses a four-step handshake to guarantee exactly one delivery.Final Answer:
QoS 2 ensures exactly once delivery. -> Option DQuick Check:
Exactly once delivery = QoS 2 [OK]
Quick Trick: Exactly once delivery requires QoS 2 handshake [OK]
Common Mistakes:
MISTAKES- Assuming QoS 1 guarantees exactly once
- Believing QoS 3 exists in MQTT
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