Overlapping Topics

Scenario 1

(all commands are sent by the same client):

1. Subscribe to A/#
2. Subscribe to A/B
3. Publish message M to topic A/B

The client will receive the message once.

Scenario 2

(all commands are sent by the same client):

1. Publish message M1 to topic A/B with retain
2. Publish message M2 to topic A/C with retain
3. Publish message M3 to topic A/D with retain
4. Subscribe to A/#

The client will receive all three of the retained messages.

Scenario 3

Given the topic tree: test test/one test/two/two

• Subscribe to test/#
• Unsubscribe from test/one
• Unsubscribe from test/two

The client will still receive messages sent to test/one and test/two. You can only unsubscribe from a topic you have explicitly subscribed to; you cannot punch holes in previous subscription.