There are a number of sample apps which can be follow.
The "simple_app" is a single application which reads data from a codelet's output channel, counts received messages, and once a counter is reached, sends the value to input channel of a different codelet.
There are two versions of this simple example: a C version and a python version. Both have identical behaviour, but have different programming models.
The "advanced_app" has two application. Both of these read and write from/to channels of codelets, but also send data between themselves.
There are two versions of this advanced example.