mosquitto qos 2 messages delivered more than once

Question

I have Mosquitto installed on Windows 8 and I am trying to write Paho clients in Java to understand MQTT. I wrote a blocking publisher and a client subscriber. I created two threads of the subscribing client with different client ids. When I publish one message with QoS 2, both the clients receive the message. I am expecting exactly one client to receive the message. Is my expectation wrong?

I felt I didn't program to the API correctly and wanted to troubleshoot with mosquitto_pub and mosquitto_sub. Same result. Both the subscribers received the message. Please check the screenshot here: https://i.stack.imgur.com/9bfUx.jpg

I am pretty sure that I am doing something wrong but I am not able to pinpoint it. All mosquitto.conf properties are set to default. Any help would be appreciated. I have exhausted half a day on this already. :(

QoS 2 means that all the published messages get delivered once and exactly once **to all the subscribers**. — kartben, Oct 19 '15 at 13:29
Thank you for clarifying! Can you post it as an answer so I can accept or upvote it? — RabbitCodes, Oct 21 '15 at 17:31

score 0 · Accepted Answer · answered Oct 21 '15 at 17:32

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QoS 2 actually means that all the published messages get delivered once and exactly once to all the subscribers.

answered Oct 21 '15 at 17:32

kartben

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mosquitto qos 2 messages delivered more than once

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