Several publishers on a single topic. How does it work?

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I would like to know how the communication works when two or more publishers are sending messages on the same topic.

I have one subscriber to an "x" topic, but it seems that the communication exists only with the node that published firstly until this node is stopped or killed and then the communication with the second publisher in the queue starts automatically. Is this the expected behaviour?

I would rather get one single message from the first publisher and afterwards another single message from the second publisher and so on. Is this possible? How can I approach this? Thank you.

Knowing that the behaviour that I wanted was the expected one, I realised that my problem was related with the queue size of my subscriber, which was smaller than the number of publishers.