C++ Boost.Asio object lifetimes

Question

asio::io_service ioService;
asio::ip::tcp::socket* socket = new asio::ip::tcp::socket(ioService);
socket->async_connect(endpoint, handler);
delete socket;

Socket's destructor should close the socket. But can the asynchronous backend handle this? Will it cancel the asynchronous operation and calling the handler? Probably not?

Answer 1

When the socket is destroyed, it invokes destroy on its service. When a SocketService's destroy() function is invoked, it cancels asynchronous operations by calling a non-throwing close() . Handlers for cancelled operations will be posted for invocation within io_service with a boost::asio::error::operation_aborted error.

---

Here is a complete example demonstrating the documented behavior:

#include <iostream>
#include <boost/asio.hpp>

void handle_connect(const boost::system::error_code& error)
{
  std::cout << "handle_connect: " << error.message() << std::endl;
}

int main()
{
  namespace ip = boost::asio::ip;
  using ip::tcp;

  boost::asio::io_service io_service;
  // Create socket with a scoped life.
  {
    tcp::socket socket(io_service);
    socket.async_connect(
        tcp::endpoint(ip::address::from_string("1.2.3.4"), 12345),
        &handle_connect);
  }
  io_service.run();
}

And its output:

handle_connect: Operation canceled

Answer 2

Why did you create the socket using new ? It won't definitely do normal process. If you really want to create the socket using new, you have to close and delete at the end of your program.

Here is a sample, just.

io_service service_;

ip::tcp::socket sock(service_);
sock.async_connect(ep, connect_handler);

deadline_timer t(service_, boost::posix_time::seconds(5));
t.async_wait(timeout_handler);

service_.run();