improve example

src/MyService.cpp

@@ -1,5 +1,10 @@
 #include "MyService.h"
 
 int MyService::add(int a, int b) {
-    return a + b;
+    counter_ += (a + b);
+    return counter_;
+}
+
+int MyService::get() {
+    return counter_;
 }

src/MyService.h

@@ -5,8 +5,13 @@
 // annotate with clang attribute or via comment annotation recognized by libclang
 // Use ANNOTATE attribute supported by clang: __attribute__((annotate("export")))
 class RPC_EXPORT MyService {
+private:
+    int counter_ = 0;
+
 public:
     RPC_EXPORT
     int add(int a, int b);
+    RPC_EXPORT
+    int get();
     int minus(int a, int b);
 };

src/client.cpp

@@ -20,6 +20,7 @@ int main() {
     ProxyMarshaller marshaller(ch);
     MyServiceProxy proxy(marshaller);
 
-    int r = proxy.add(7, 9);
-    std::cout << "RESULT: " << r << std::endl;
+    proxy.add(7, 9);
+    int counter = proxy.get();
+    std::cout << "RESULT: " << counter << std::endl;
 }