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Trivial applications
====================
.. note::
To successfully run the following examples, please make sure that NFD is properly
configured and running. For more information about NFD, refer to `NFD's official
homepage <https://named-data.net/doc/NFD/>`_.
Trivial consumer
----------------
In the following trivial example, a consumer creates a :ndn-cxx:`Face` with default
transport (:ndn-cxx:`UnixTransport`) and sends an Interest for
``/localhost/testApp/randomData``. While expressing Interest, the app specifies three
callbacks to be called when Data/Nack is retrieved or Interest times out.
.. literalinclude:: ../examples/consumer.cpp
:language: c++
:linenos:
:emphasize-lines: 39-45,48,59,65,71
Trivial producer
----------------
The following example demonstrates how to write a simple producer application.
First, the application sets an Interest filter for ``/localhost/testApp`` to receive all
Interests that have this prefix. The :ndn-cxx:`Face::setInterestFilter` call accepts two
callbacks; the first will be called when an Interest is received and the second if prefix
registration fails.
After an Interest is received, the producer creates a Data packet with the same name as
the received Interest, adds content, and signs it with the system-default identity. It is
also possible to specify a particular key to be used during the signing. For more
information, refer to :ndn-cxx:`KeyChain API documentation <KeyChain>`.
Finally, after Data packet has been created and signed, it is returned to the requester
using :ndn-cxx:`Face::put` method.
.. literalinclude:: ../examples/producer.cpp
:language: c++
:linenos:
:emphasize-lines: 41,50,57-59,62,70,74
Consumer that uses Scheduler
----------------------------
The following example demonstrates how to use :ndn-cxx:`Scheduler` to schedule arbitrary
events for execution at specific points of time.
The library internally uses `boost::asio::io_service
<https://www.boost.org/doc/libs/1_65_1/doc/html/boost_asio/reference/io_service.html>`_ to
implement fully asynchronous NDN operations (i.e., sending and receiving Interests and
Data). In addition to network-related operations, ``boost::asio::io_service`` can be used
to execute any arbitrary callback within the processing thread (run either explicitly via
``io_service::run()`` or implicitly via :ndn-cxx:`Face::processEvents` as in previous
examples). :ndn-cxx:`Scheduler` is just a wrapper on top of ``io_service``, providing a
simple interface to schedule tasks at specific times.
The highlighted lines in the example demonstrate all that is needed to express a second
Interest approximately 3 seconds after the first one.
.. literalinclude:: ../examples/consumer-with-timer.cpp
:language: c++
:linenos:
:emphasize-lines: 39-40,56,62,93,106,114-116