== '''The Ping-Pong Example''' ==


To help getting into using Ariba, we provide a short example of how to use the architecture. For this, assume a simple service whose simply and only intention is to exchange data packets between two participating nodes, just like playing ping pong. You will find the whole code within the package under ''sample/pingpong''.

The source files divide into the main code (''PingPong.h/.cpp'') and the used message format (declared in ''PingPongMessage.h/.cpp''). In Addition, ''main.cpp'' acts as the entry point to the ping-pong example. We will first give a high-level introduction about what the example does and later dig deeper into the code. 

'''What it does'''
As already mentioned, the example service simply exchanges packets between two participating network nodes. This is accomplished by using the ''Ariba'' abstraction to create a communication context and hide underlay details. The participants form a ''SpoVNet'' instance in which the first one (as the initiator) creates the instance, while the second joins. As soon as the second has successfully joined the instance, it starts sending packets to the initiator periodically. When such a packet reaches the latter, he responds by also sending a packet back. This procedure repeats, until a button is pressed. 

'''How it does it'''
Let's take a look at the code now. Writing a service is pretty simple when using ''Ariba'' because most difficulties and annoyances that could come up when struggling with writing network code are taken from the developer. We start with the ''main.cpp''.


{{{
01 #include <string>
02 #include "ariba/utility/startup/StartupWrapper.h"
03 #include "PingPong.h"
04
05 using std::string;
06 using ariba::utility::StartupWrapper;
07 using ariba::application::pingpong::PingPong;
08
09 int main( int argc, char** argv ) {
10
11	string config = "../etc/settings.cnf";
12	if (argc >= 2) config = argv[1];
13
14	StartupWrapper::initConfig( config );
15	StartupWrapper::initSystem();
16	
17	// this will do the main functionality and block
18	PingPong ping;
19	ping.setMode( !Configuration::instance().read<bool>("GENERAL_Initiator") );
20	StartupWrapper::startup(&ping, true);
21
22	// this will run blocking until <enter> is hit
23
24	StartupWrapper::shutdown();
25	return 0;
26 }
}}}
The ''main.cpp'' serves us as an entry point to the application. In the first lines we include class definitions we need here (e.g. strings because we want to handle some). Also, we include the StartupWrapper class that comes with ''Ariba''. It provides some handy helpers for initialization. Finally, we need to include the PingPong.h, because this is the actual thing we want to execute.
Then, we declare the used namespaces (lines 05-07) to be able to use the functionalities.