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 !!!!!  }};