Callback not invoked when using share subscription if publish and subscribe message on the same host

Hello everyone

Recently I use MQTT java paho client API, version is MQTTv5 1.2.5 on my local maven project.

I found a very strange issue:

If publish message to the topic and then subscribe this topic on the same host, it can not receive message usually, which callback is not invoked.

However, if publish messages to the topic on other host, then it will succeed to subscribe the topic and receive messages.

I don't know whether any others encounter this issue.

Looking forward to your reply.

Thanks you!

- [ ] Bug exists Release Version 1.2.5 ( Master Branch)
- [ ] Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

Start by reproducing the report with the MQTT v5 Java client 1.2.5: publish and subscribe to the same topic on one host, then compare it with publishing from another host. Trace the subscription callback path and determine why the same-host case does not invoke it. Done means the callback reliably receives the message in both scenarios.

Written by the indexing model from the issue text.