Example

#ifndef GTKMM_EXAMPLE_SERVER_H
#define GTKMM_EXAMPLE_SERVER_H

#include <sigc++/sigc++.h>

class Server
{
public:
  Server();
  virtual ~Server();

  void do_something();

  //signal accessor:
  using type_signal_something = sigc::signal<void(bool, int)>;
  type_signal_something signal_something();

protected:
  type_signal_something m_signal_something;
};

#endif //GTKMM_EXAMPLE_SERVER_H

#ifndef GTKMM_EXAMPLE_CLIENT_H
#define GTKMM_EXAMPLE_CLIENT_H

#include <sigc++/sigc++.h>

//Client must inherit from sigc::trackable.
//because libsigc++ needs to keep track of the lifetime of signal handlers.
class Client : public sigc::trackable
{
public:
  Client();
  virtual ~Client();

  //Signal handler:
  void on_server_something(bool a, int b);
};

#endif //GTKMM_EXAMPLE_CLIENT_H

#include "server.h"
#include "client.h"
#include <iostream>

int main(int, char**)
{
  Server server;
  Client client;

  //Connect a Server signal to the signal handler in Client.
  server.signal_something().connect(sigc::mem_fun(client,
              &Client::on_server_something) );

  std::cout << "Before Server::do_something()" << std::endl;

  //Tell the server to do something that will eventually cause it to emit the
  //"something" signal.
  server.do_something();    // Client::on_server_something() will run before
                            // Server::do_something() has completed.

  std::cout << "After Server::do_something()" << std::endl;

  return 0;
}

#include "server.h"
#include <iostream>

Server::Server()
{
}

Server::~Server()
{
}

Server::type_signal_something Server::signal_something()
{
  return m_signal_something;
}

void Server::do_something()
{
  m_signal_something.emit(false, 5);
}

#include "client.h"
#include <iostream>

Client::Client()
{
}

Client::~Client()
{
}

void Client::on_server_something(bool a, int b)
{
  std::cout << "Client::on_server_something() called with these parameters: "
      << a << ", " << b << std::endl;
}