Implementation of the Client entity in the echo example
The code of the Client entity uses the transport types and methods that will be generated during the solution build by the NK compiler based on the IDL description of the Ping interface.
However, to obtain the descriptions of types and signatures of methods required for implementing the entity, you can use the NK compiler immediately after creating an EDL description of the entity, CDL descriptions of components and IDL descriptions of the interfaces used for interaction. As a result, the required types and signatures of methods will be declared in the generated *.h files.
In the Client entity implementation, the following is required:
- Get the client IPC handle of the connection (channel) by using the
ServiceLocatorConnect()function.Input the name of the IPC
server_connectionpredefined in the init.yaml file. - Initialize
NkKosTransportby passing the obtained IPC handle to theNkKosTransport_Init()function. - Obtain the ID of the required interface (
RIID) by using theServiceLocatorGetRiid()function. - Input the full name of the
Pinginterface implementation. It consists of the names of the component instance (Echo.ping) and interface (ping) that were previously defined in Server.edl and Ping.cdl. - Initialize the proxy object by passing the transport and interface ID to the
Ping_proxy_init()function. - Prepare the request and response structures.
- Call the
Ping_Ping()interface method by passing the proxy object and the pointers to the request and response.
client.c
/* Files required for transport initialization. */
/* Description of the server interface used by the client entity. */
/* Client entity entry point. */
int main(int argc, const char *argv[])
{
NkKosTransport transport;
struct echo_Ping_proxy proxy;
int i;
fprintf(stderr, "Hello I'm client\n");
/* Get client IPC handle of
* "server_connection". */
Handle handle = ServiceLocatorConnect("server_connection");
assert(handle != INVALID_HANDLE);
/* Initialize IPC transport for interaction with the server entity. */
NkKosTransport_Init(&transport, handle, NK_NULL, 0);
/* Get Runtime Interface ID (RIID) for interface echo.Ping.ping.
* Here ping is the name of the echo.Ping component instance,
* echo.Ping.ping is the name of the Ping interface implementation. */
nk_iid_t riid = ServiceLocatorGetRiid(handle, "echo.Ping.ping");
assert(riid != INVALID_RIID);
/* Initialize proxy object by specifying transport (&transport)
* and ID of the server interface (riid). Each method
* of the proxy object will be implemented by sending a request to the server. */
echo_Ping_proxy_init(&proxy, &transport.base, riid);
/* Request and response structures */
echo_Ping_Ping_req req;
echo_Ping_Ping_res res;
/* Test loop. */
req.value = EXAMPLE_VALUE_TO_SEND;
for (i = 0; i < 10; ++i)
{
/* Call Ping interface method.
* Server will be sent a request for calling Ping interface method
* ping_comp.ping_impl with the value argument. Calling thread is locked
* until a response is received from the server. */
if (echo_Ping_Ping(&proxy.base, &req, NULL, &res, NULL) == rcOk)
{
/* Print "result" value from response
* (result is the output argument of the Ping method). */
fprintf(stderr, "result = %d\n", (int) res.result);
/* Include received "result" value into "value" argument
* to resend to server in next iteration. */
req.value = res.result;
}
else
fprintf(stderr, "Failed to call echo.Ping.Ping()\n");
}
return EXIT_SUCCESS;
}