问题
What exactly does the destructor of boost::asio::ip::tcp::socket do? I can't tell, even after scouring Boost docs and source code, if I need to use
socket->shutdown(boost::asio::ip::tcp::socket::shutdown_both);
socket->close();
before calling
delete socket;
Do I need to close the socket manually, or does the destructor handle this?
回答1:
When a socket is destroyed, it will be closed as-if by socket.close(ec) during the destruction of the socket.
I/O objects, such as socket, derive from basic_io_object. Within the basic_io_object destructor, destroy() will be invoked on the I/O object's I/O service, passing in an instance of the implementation_type on which the I/O object's service will operate. In the case of socket, destroy() will be invoked on a type that fulfills the SocketService type requirement, closing the underlying socket. In the documentation below, a is an instance of a socket service class, and b is an instance of the implementation_type for the socket service class:
a.destroy(b):[...] Implicitly cancels asynchronous operations, as if by calling
a.close(b, ec).
a.close(b, ec):If
a.is_open()is true, causes any outstanding asynchronous operations to complete as soon as possible. Handlers for cancelled operations shall be passed the error codeerror::operation_aborted.post:
!a.is_open(b).
回答2:
No you don't need to close it. Though it might be cleaner to do so, if you want to report any errors surrounding protocol shutdown.
The destructor just /appears/ to be empty, that's a good sign of Modern C++:
- http://en.cppreference.com/w/cpp/language/rule_of_three
- Rule Of Zero
回答3:
The answers have skipped over the issue of shutdown(). From the close() documentation, "For portable behaviour with respect to graceful closure of a connected socket, call shutdown() before closing the socket".
If deleting the socket does an implicit close, it seems that a call to shutdown() is still recommended before deleting it.
来源：https://stackoverflow.com/questions/39813066/boost-asio-socket-destructor-closes-connection