I want to subscribe to topic that is not duplicated.

I test this case.

1. A receiver connect to server, 'clean session' is false.
2. The receiver subscribe to same topic many times.
3. A Sender publish a message to the topic.
4. Receiver receive duplicate message.

If the receiver subscribe three times on case #2, receive three messages on case #4.

I want to subscribe to topic is not duplicated.
It is impossible that subscribe only once. Because receiver can't know that sender has subscription data of receiver.
If receiver write subscription record in receiver's memory and use it, couldn't receive any message after that sender clean session.