This example project demonstrates how to access Homegear's IPC (= Inter-process Communication) interface. It registers two RPC methods in Homegear (exampleTest1() and exampleTest2()). exampleTest1() prints a line to the terminal and returns a string containing the current timestamp. exampleTest2() expects a string as parameter, also prints a line to the terminal and returns the length of the string.

Before starting, either compile libhomegear-ipc or on Debian, Raspbian or Ubuntu install it with:

apt install libhomegear-ipc

To compile, just execute:

./makeDebug.sh

To test, you can call the newly registerd RPC methods from the shell:

homegear -e rc 'print_v($hg->exampleTest1());'
homegear -e rc 'print_v($hg->exampleTest2("Hello"));'

All RPC methods known by Homegear can be called by executing invoke(). The signature is:

Ipc::PVariable invoke(std::string methodName, Ipc::PArray parameters);

The first parameter is the name of the RPC method (e. g. getValue()). The second parameter is a vector of Ipc::PVariable (= a std::shared_ptr to Ipc::Variable). Ipc::Variable is a class which can contain values of any type. The usage should be self-explaining.

For example to create the parameters array for getValue(12, 1, "STATE"), call:

Ipc::PArray parameters = std::make_shared<Ipc::Array>();
parameters->reserve(3);

To avoid copy operations, we reserve space for 3 elements.

Now we add the parameters (peer ID, channel and variable name):

parameters->push_back(std::make_shared<Ipc::Variable>(12));
parameters->push_back(std::make_shared<Ipc::Variable>(1));
parameters->push_back(std::make_shared<Ipc::Variable>("HUMIDITY"));

Call invoke() and print out the result:

Ipc::PVariable result = invoke("getValue", parameters);
std::cout << "Result: " << result->integerValue << std::endl;