Boost C++ Libraries of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the master branch, built from commit b5c99c1c90.


Close a socket or socket-like object.


Defined in header <boost/beast/core/stream_traits.hpp>

    class Socket>
    Socket& sock);

This function attempts to close an object representing a socket. In this context, a socket is an object for which an unqualified call to the function void beast_close_socket(Socket&) is well-defined. The function beast_close_socket is a customization point, allowing user-defined types to provide an algorithm for performing the close operation by overloading this function for the type in question. Since the customization point is a function call, the normal rules for finding the correct overload are applied including the rules for argument-dependent lookup ("ADL"). This permits classes derived from a type for which a customization is provided to inherit the customization point. An overload for the networking class template net::basic_socket is provided, which implements the close algorithm for all socket-like objects (hence the name of this customization point). When used in conjunction with get_lowest_layer, a generic algorithm operating on a layered stream can perform a closure of the underlying socket without knowing the exact list of concrete types.

Example 1

The following generic function synchronously sends a message on the stream, then closes the socket.

template <class WriteStream>
void hello_and_close (WriteStream& stream)
    net::write(stream, net::const_buffer("Hello, world!", 13));

To enable closure of user defined types, it is necessary to provide an overload of the function beast_close_socket for the type.

Example 2

The following code declares a user-defined type which contains a private socket, and provides an overload of the customization point which closes the private socket.

class my_socket
    net::ip::tcp::socket sock_;

    my_socket(net::io_context& ioc)
        : sock_(ioc)

    friend void beast_close_socket(my_socket& s)
        error_code ec;
        // ignore the error




The socket to close. If the customization point is not defined for the type of this object, or one of its base classes, then a compiler error results.

See Also