Destroying Boost Asio socket without closing native handler

Question

I am facing the following issue. I am trying to use a third party library with boost Asio and I need to inject some of the socket descriptors used by the library in io_service event loop.

The approach I use is creating a boost::asio::ip::tcp::socket passing the native handler my library provides.

Problem is that library would just communicate it is not interested in a particular socket notifications (which means that library may close the socket or reuse it at a later point). In any case, I would like to do a clean up of boost sockets and destroy them, but without closing the native handler (i.e. file descriptor).

In short, is there any way of destroying a boost::asio::ip::tcp::socket without closing the underlying handler? I am aware of using posix::stream_descriptor instead, but I would like my solution to be portable.

Did you try to assign a dumb socket, even if it fails may be previous will be no more available... — Jean Davy
@JeanDavy socket.assign(protocol, native) has a pre-condition that socket is not open (see the SocketService). If this precondition is not met, then the state of socket remains unchanged. — Tanner Sansbury

Tanner Sansbury Tanner Sansbury · Accepted Answer · 2016-08-12T14:37:11

No. There is no way to destroy ip::tcp::socket without closing the native handler. This cannot be portable implemented, and therefore Asio does not support it. In particular, prior to Windows 8.1, once a socket is associated with an I/O completion port, the socket can only be disassociated by closing it¹. See this related github issue where Chris Kohlhoff responds to this feature request:

This is not supported because it cannot be portably implemented. Specifically, on Windows a socket is associated to an I/O completion port and cannot be disassociated.

If you are only targeting POSIX-based systems then perhaps you can stick the descriptor into a posix::stream_descriptor instead? This class does provide a release() member function.

_{1. Windows 8.1 enabled removing the completion port association via FileReplaceCompletionInformation without closing the socket.}

Destroying Boost Asio socket without closing native handler

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