grpc_invoke_np -  Executes an RPC.
  grpc_error_t grpc_invoke_np(grpc_object_handle_t_np *handle, char *method_name, ...)
  grpc_object_handle_t_np *handle  char *method_nameOther argumentsThe grpc_invoke_np() function calls the method defined by the object handle. The grpc_invoke_np() function is blocked until execution of the called method is completed.
This function is MT-safe.
If successful, GRPC_NO_ERROR is returned. In the case of an error, Error code is returned.
  GRPC_NOT_INITIALIZED  GRPC_SERVER_NOT_FOUND  GRPC_FUNCTION_NOT_FOUND  GRPC_INVALID_OBJECT_HANDLE_NP  GRPC_RPC_REFUSED  GRPC_COMMUNICATION_FAILED  GRPC_TIMEOUT_NP  GRPC_OTHER_ERROR_CODE