Waits. For message receptions, rmw_wait must be performed. On this call, rmw_microxrcedds will ask all the publications to get new data from their topics. That request uses the Micro XRCE-DDS request data function, which asks the Micro XRCE-DDS Agent for the latest messages on the topics. After requesting data, rmw_microxrcedds waits on the Micro XRCE-DDS session till a timeout occurs or at least one new topic message arrived. The subscription is flagged as pending to read data from. Once the wait gets triggered, a take data is called for the subscription with new messages. This call deserialises the data using the type support provided to the subscription on its creation and passes the deserialised data to the upper layers which will call the user callback.
