.. _pingpong:

====================
 Example: Ping Pong
====================

This example creates two different nodes, ``Ping`` and ``Pong``. The first node
is executed with a fixed timing (see :ref:`Timed processing <procstrat>`) and
sends a "Ping!" event over its output port. The second component listens to its
input port and answers with a "Pong!".

#. At first a Ping node is defined (lines 15-34). The node has one output port
   to send a string (line 30). In its main processing method it prints a
   "Ping!" to the console and sends the string over its output port (line 26).
#. Then a Pong node is defined (lines 36-53). The node has one input port
   to receive a string (line 47). In its main processing method it prints a
   "Pong!" as answer.
#. In the main function of this example we create a ping node and configure it
   to be timed (line 66, see :ref:`Timed <procstrat>`) and we
   configure the output port to send to the scope ``/ping`` (line 67).
#. A pong node is created and configured to be triggered when an input arrives
   at its input port (line 71, see :ref:`Port-Triggered <procstrat>`)
   and we configure the input port to listen to the scope ``/ping``.
#. To run the program we need to send a timing signal to the ping node. We
   create a :ref:`beat` and assign the ping node to it (lines 75-76).
   The pong node will be triggered by incoming input.

*Note:* You can inspect the application with the :ref:`RSB Logger <rsb:logger>`,
since the output scope of the Ping node is configured to also send over a remote
transport. This should show an event with ``10Hz`` on the ``/ping`` scope.
The input port of the pong node is configured to be only local, because
otherwise the node would receive every event twice (over the local *and* the
remote transport). 

.. literalinclude:: ../../examples/pingPong.cpp
   :language: c++
   :emphasize-lines: 16-35,37-54,67-68,72,76-77
   :linenos: