I'm looking for suggestions regarding RPC libraries implemented in C++, for C++ developers.

Some requirements constraints:

• Should work on both linux/unix and win32 systems
• Be able to execute free function and class methods
• Hopefully written in modern C++ not 90's/java-esque C++
• Be able to function over networks and hetrogenous architectures
• Not too slow or inefficient
• Hopefully provide interfaces for TR1 style std::function's et al.

My example usage is to invoke the free function foo on a remote machine.

---snip---
// foo translation unit
int foo(int i, int j)
{
   return i + j;
}
---snip---


---snip---
// client side main
int main()
{
   //register foo on client and server
   //setup necassary connections and states

   int result;

   if (RPCmechanism.invoke("foo",4,9,result))
      std::cout << "foo(4,9) = " result << std::endl;
   else
      std::cout << "failed to invoke foo(4,9)!" << std::endl;

   return 0;
}
---snip---

Something that can achieve the above or similar would be great.