defmodule App1.Calculator do
  use GenServer

  def add( num1, num2 ), do: GenServer.call( App1.Caclculator, {:add, num1, num2})

  def handle_call({:add, num1, num2}, _from, state) do
    {:reply, {:ok, num1+num2}, state}
  end
end

defmodule App1.Calculator do
  use GenServer

  def handle_call({:add, num1, num2}, _from, state) do
    {:reply, {:ok, num1+num2}, state}
  end
end

defmodule Service.Calculator do
  def add(num1, num2), do: GenServer.call(process_name, {:add, num1, num2})

  # Just an example of how you might have named your node and calculator process
  def process_name, do: {:calculator, :"app1@127.0.0.1"}
end