terminate called after throwing an instance of 'boost::exception_detail::clone_impl<std::__exception_ptr::exception_ptr>'

struct hello_world {
  /*<< This is the function that handles the incoming request. >>*/
  void operator()(server::request const &request, server::connection_ptr response) {
    server::string_type ip = source(request);
    unsigned int port = request.source_port;
    std::ostringstream data;
    
    data << "Hello, " << ip << ':' << port << '!';
    response->write(data.str());     // where the problem occurs !!!!!
  }
};