Miss the 1st one

[jinfeihan57]

I am a new user of dds. when I run example PublishHelloWorld->SubscribeHelloWorld or CustomTransports->SubscribeHelloWorld. The first topic is lost almost every time. I want to know WHY? and how to fix this. Thanks.

[pablogs9]

You can create your entities with transient local QoS and a certain amount of history in order to ensure the reception of all samples. You can learn more about QoS in the Fast DDS documentation: https://fast-dds.docs.eprosima.com/en/latest/fastdds/rtps_layer/rtps_layer.html?highlight=TRANSIENT_LOCAL#setting-the-data-durability-kind

[jinfeihan57]

You can create your entities with transient local QoS and a certain amount of history in order to ensure the reception of all samples. You can learn more about QoS in the Fast DDS documentation: https://fast-dds.docs.eprosima.com/en/latest/fastdds/rtps_layer/rtps_layer.html?highlight=TRANSIENT_LOCAL#setting-the-data-durability-kind

VOLATILE (default): Messages are discarded as they are sent. If a new Reader matches after message n, it will start received from message n+1. I start the Subscribe first, when MicroXRCEAgent found Subscribe, then I start Publish. this should not topic miss.

[pablogs9]

Ok, provide feedback and close if the issue is solved.

[jinfeihan57]

It did not solve my issue.

[pablogs9]

What else do you need beyond modifying the QoS of your entities?

[jinfeihan57]

I didn't change anything.

[pablogs9]

Well, when you change the code to apply the required QoS, then, provide feedback and close if the issue is solved.