Polling Read

Concept

In RTI Connext there are three ways to receive data:

• Your application can explicitly check for new data by calling a DataReader's read() or take() method. This method is also known as polling for data.
• Your application can be notified asynchronously whenever new data samples arrive--this is done with a Listener on either the Subscriber or the DataReader. Connext will invoke the Listener's callback routine when there is new data. Within the callback routine, user code can access the data by calling read() or take() on the DataReader. This method is the way for your application to receive data with the least amount of latency.
• Your application can wait for new data by using Conditions and a WaitSet, then calling wait(). Connext will block your application's thread until the criteria (such as the arrival of samples, or a specific status) set in the Condition becomes true. Then your application resumes and can access the data with read() or take().

In this example we focus on the first of these options -- polling read.

Example Description

The example implements a publisher application that sends a random number as data every second. A subscriber application polls for data once every five seconds and computes the average of all examples received in that period.

Note that using polling read instead of getting data via callbacks, means that the processing occurs in the context of the application's main() rather than in the DDS receive thread.

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