Using mosquitto_pub WITH mosquitto_sub on AWS IoT thing is not working

Question

Strange problem when trying to interact with an AWS IoT thing using the mosquitto CLI clients:

• mosquitto_pub works as I can see the incoming message in the AWS IoT Test console.
• mosquitto_sub works as I can receive messages sent from the AWS IoT Test console.

However, mosquitto_sub doesn't receive messages sent using mosquitto_pub.

Publisher:

mosquitto_pub --cert krc-test1.cert.pem --key krc-test1.private.key --cafile root-CA.crt -h (endpoint)-ats.iot.us-east-1.amazonaws.com -t topic_1 -m Hello -i basicPubSub

'Hello' will be received in the AWS IoT Test console.

Subscriber:

mosquitto_sub --cert krc-test1.cert.pem --key krc-test1.private.key --cafile root-CA.crt -h (endpoint)-ats.iot.us-east-1.amazonaws.com -t topic_1 -v -i basicPubSub -d

Will receive messages sent from the AWS IoT Test console, but not from the publisher above. Instead, the subscriber will output this ~1 sec after the message is sent:

Client basicPubSub sending CONNECT
Client basicPubSub received CONNACK (0)
Client basicPubSub sending SUBSCRIBE (Mid: 7, Topic: topic_1, QoS: 0)
Client basicPubSub received SUBACK
Subscribed (mid: 7): 0

Anyone has a clue about what might be going on?

Note: I'm using the clientID 'basicPubSub' and the pre-configured topic 'topic_1' for convenience as they are pre-configured in the base policy.

Answer 1

You shouldn't use the same client id for both mosquitto apps.

Client id's need to be unique, so you'll have to add a new one to the policy.