...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Close a socket or socket-like object.
Defined in header <boost/beast/core/stream_traits.hpp>
template< class Socket> void close_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.
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)); close_socket(get_lowest_layer(stream)); }
To enable closure of user defined types, it is necessary to provide an overload
of the function beast_close_socket
for the type.
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_; public : my_socket(net::io_context& ioc) : sock_(ioc) { } friend void beast_close_socket(my_socket& s) { error_code ec; s.sock_.close(ec); // ignore the error } };
Name |
Description |
---|---|
|
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. |