[Solved] A developer writes this code: client.publish('sensor/temp', '25', qos=1) client.publish('sensor/temp', '26', qos=1) But only the first message is received by the subscriber. What could be the problem? | Raspberry Pi

Raspberry Pi - MQTT for IoT

A developer writes this code:

client.publish('sensor/temp', '25', qos=1)
client.publish('sensor/temp', '26', qos=1)

But only the first message is received by the subscriber. What could be the problem?

AThe topic name is invalid.

BThe client did not call loop_start() or loop_forever() to process network events.

CQoS 1 does not guarantee message delivery.

DThe payload must be numeric, not string.

Step-by-Step Solution

Solution:

Step 1: Understand Paho MQTT client network processing
Publishing requires the client network loop to run to send and receive packets.
Step 2: Identify missing network loop call
If loop_start() or loop_forever() is not called, messages may not be sent properly.
Final Answer:
The client did not call loop_start() or loop_forever() to process network events. -> Option B
Quick Check:
Network loop must run to send QoS messages [OK]

Quick Trick: Always run client.loop_start() or loop_forever() [OK]

Common Mistakes:

MISTAKES

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