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 //
 // basic_socket_acceptor.hpp
 // ~~~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
 #ifndef BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_HPP
 #define BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_HPP
 
 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
 # pragma once
 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
 
 #include <utility>
 #include <boost/asio/detail/config.hpp>
 #include <boost/asio/any_io_executor.hpp>
 #include <boost/asio/basic_socket.hpp>
 #include <boost/asio/detail/handler_type_requirements.hpp>
 #include <boost/asio/detail/io_object_impl.hpp>
 #include <boost/asio/detail/non_const_lvalue.hpp>
 #include <boost/asio/detail/throw_error.hpp>
 #include <boost/asio/detail/type_traits.hpp>
 #include <boost/asio/error.hpp>
 #include <boost/asio/execution_context.hpp>
 #include <boost/asio/socket_base.hpp>
 
 #if defined(BOOST_ASIO_WINDOWS_RUNTIME)
 # include <boost/asio/detail/null_socket_service.hpp>
 #elif defined(BOOST_ASIO_HAS_IOCP)
 # include <boost/asio/detail/win_iocp_socket_service.hpp>
 #elif defined(BOOST_ASIO_HAS_IO_URING_AS_DEFAULT)
 # include <boost/asio/detail/io_uring_socket_service.hpp>
 #else
 # include <boost/asio/detail/reactive_socket_service.hpp>
 #endif
 
 #include <boost/asio/detail/push_options.hpp>
 
 namespace boost {
 namespace asio {
 
 #if !defined(BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_FWD_DECL)
 #define BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_FWD_DECL
 
 // Forward declaration with defaulted arguments.
 template <typename Protocol, typename Executor = any_io_executor>
 class basic_socket_acceptor;
 
 #endif // !defined(BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_FWD_DECL)
 
 /// Provides the ability to accept new connections.
 /**
  * The basic_socket_acceptor class template is used for accepting new socket
  * connections.
  *
  * @par Thread Safety
  * @e Distinct @e objects: Safe.@n
  * @e Shared @e objects: Unsafe.
  *
  * Synchronous @c accept operations are thread safe, if the underlying
  * operating system calls are also thread safe. This means that it is permitted
  * to perform concurrent calls to synchronous @c accept operations on a single
  * socket object. Other synchronous operations, such as @c open or @c close, are
  * not thread safe.
  *
  * @par Example
  * Opening a socket acceptor with the SO_REUSEADDR option enabled:
  * @code
  * boost::asio::ip::tcp::acceptor acceptor(my_context);
  * boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::tcp::v4(), port);
  * acceptor.open(endpoint.protocol());
  * acceptor.set_option(boost::asio::ip::tcp::acceptor::reuse_address(true));
  * acceptor.bind(endpoint);
  * acceptor.listen();
  * @endcode
  */
 template <typename Protocol, typename Executor>
 class basic_socket_acceptor
   : public socket_base
 {
 private:
   class initiate_async_wait;
   class initiate_async_accept;
   class initiate_async_move_accept;
 
 public:
   /// The type of the executor associated with the object.
   typedef Executor executor_type;
 
   /// Rebinds the acceptor type to another executor.
   template <typename Executor1>
   struct rebind_executor
   {
     /// The socket type when rebound to the specified executor.
     typedef basic_socket_acceptor<Protocol, Executor1> other;
   };
 
   /// The native representation of an acceptor.
 #if defined(GENERATING_DOCUMENTATION)
   typedef implementation_defined native_handle_type;
 #elif defined(BOOST_ASIO_WINDOWS_RUNTIME)
   typedef typename detail::null_socket_service<
     Protocol>::native_handle_type native_handle_type;
 #elif defined(BOOST_ASIO_HAS_IOCP)
   typedef typename detail::win_iocp_socket_service<
     Protocol>::native_handle_type native_handle_type;
 #elif defined(BOOST_ASIO_HAS_IO_URING_AS_DEFAULT)
   typedef typename detail::io_uring_socket_service<
     Protocol>::native_handle_type native_handle_type;
 #else
   typedef typename detail::reactive_socket_service<
     Protocol>::native_handle_type native_handle_type;
 #endif
 
   /// The protocol type.
   typedef Protocol protocol_type;
 
   /// The endpoint type.
   typedef typename Protocol::endpoint endpoint_type;
 
   /// Construct an acceptor without opening it.
   /**
    * This constructor creates an acceptor without opening it to listen for new
    * connections. The open() function must be called before the acceptor can
    * accept new socket connections.
    *
    * @param ex The I/O executor that the acceptor will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the
    * acceptor.
    */
   explicit basic_socket_acceptor(const executor_type& ex)
     : impl_(0, ex)
   {
   }
 
   /// Construct an acceptor without opening it.
   /**
    * This constructor creates an acceptor without opening it to listen for new
    * connections. The open() function must be called before the acceptor can
    * accept new socket connections.
    *
    * @param context An execution context which provides the I/O executor that
    * the acceptor will use, by default, to dispatch handlers for any
    * asynchronous operations performed on the acceptor.
    */
   template <typename ExecutionContext>
   explicit basic_socket_acceptor(ExecutionContext& context,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
     : impl_(0, 0, context)
   {
   }
 
   /// Construct an open acceptor.
   /**
    * This constructor creates an acceptor and automatically opens it.
    *
    * @param ex The I/O executor that the acceptor will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the
    * acceptor.
    *
    * @param protocol An object specifying protocol parameters to be used.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   basic_socket_acceptor(const executor_type& ex, const protocol_type& protocol)
     : impl_(0, ex)
   {
     boost::system::error_code ec;
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     boost::asio::detail::throw_error(ec, "open");
   }
 
   /// Construct an open acceptor.
   /**
    * This constructor creates an acceptor and automatically opens it.
    *
    * @param context An execution context which provides the I/O executor that
    * the acceptor will use, by default, to dispatch handlers for any
    * asynchronous operations performed on the acceptor.
    *
    * @param protocol An object specifying protocol parameters to be used.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   template <typename ExecutionContext>
   basic_socket_acceptor(ExecutionContext& context,
       const protocol_type& protocol,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value,
         defaulted_constraint
       > = defaulted_constraint())
     : impl_(0, 0, context)
   {
     boost::system::error_code ec;
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     boost::asio::detail::throw_error(ec, "open");
   }
 
   /// Construct an acceptor opened on the given endpoint.
   /**
    * This constructor creates an acceptor and automatically opens it to listen
    * for new connections on the specified endpoint.
    *
    * @param ex The I/O executor that the acceptor will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the
    * acceptor.
    *
    * @param endpoint An endpoint on the local machine on which the acceptor
    * will listen for new connections.
    *
    * @param reuse_addr Whether the constructor should set the socket option
    * socket_base::reuse_address.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @note This constructor is equivalent to the following code:
    * @code
    * basic_socket_acceptor<Protocol> acceptor(my_context);
    * acceptor.open(endpoint.protocol());
    * if (reuse_addr)
    *   acceptor.set_option(socket_base::reuse_address(true));
    * acceptor.bind(endpoint);
    * acceptor.listen();
    * @endcode
    */
   basic_socket_acceptor(const executor_type& ex,
       const endpoint_type& endpoint, bool reuse_addr = true)
     : impl_(0, ex)
   {
     boost::system::error_code ec;
     const protocol_type protocol = endpoint.protocol();
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     boost::asio::detail::throw_error(ec, "open");
     if (reuse_addr)
     {
       impl_.get_service().set_option(impl_.get_implementation(),
           socket_base::reuse_address(true), ec);
       boost::asio::detail::throw_error(ec, "set_option");
     }
     impl_.get_service().bind(impl_.get_implementation(), endpoint, ec);
     boost::asio::detail::throw_error(ec, "bind");
     impl_.get_service().listen(impl_.get_implementation(),
         socket_base::max_listen_connections, ec);
     boost::asio::detail::throw_error(ec, "listen");
   }
 
   /// Construct an acceptor opened on the given endpoint.
   /**
    * This constructor creates an acceptor and automatically opens it to listen
    * for new connections on the specified endpoint.
    *
    * @param context An execution context which provides the I/O executor that
    * the acceptor will use, by default, to dispatch handlers for any
    * asynchronous operations performed on the acceptor.
    *
    * @param endpoint An endpoint on the local machine on which the acceptor
    * will listen for new connections.
    *
    * @param reuse_addr Whether the constructor should set the socket option
    * socket_base::reuse_address.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @note This constructor is equivalent to the following code:
    * @code
    * basic_socket_acceptor<Protocol> acceptor(my_context);
    * acceptor.open(endpoint.protocol());
    * if (reuse_addr)
    *   acceptor.set_option(socket_base::reuse_address(true));
    * acceptor.bind(endpoint);
    * acceptor.listen();
    * @endcode
    */
   template <typename ExecutionContext>
   basic_socket_acceptor(ExecutionContext& context,
       const endpoint_type& endpoint, bool reuse_addr = true,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
     : impl_(0, 0, context)
   {
     boost::system::error_code ec;
     const protocol_type protocol = endpoint.protocol();
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     boost::asio::detail::throw_error(ec, "open");
     if (reuse_addr)
     {
       impl_.get_service().set_option(impl_.get_implementation(),
           socket_base::reuse_address(true), ec);
       boost::asio::detail::throw_error(ec, "set_option");
     }
     impl_.get_service().bind(impl_.get_implementation(), endpoint, ec);
     boost::asio::detail::throw_error(ec, "bind");
     impl_.get_service().listen(impl_.get_implementation(),
         socket_base::max_listen_connections, ec);
     boost::asio::detail::throw_error(ec, "listen");
   }
 
   /// Construct a basic_socket_acceptor on an existing native acceptor.
   /**
    * This constructor creates an acceptor object to hold an existing native
    * acceptor.
    *
    * @param ex The I/O executor that the acceptor will use, by default, to
    * dispatch handlers for any asynchronous operations performed on the
    * acceptor.
    *
    * @param protocol An object specifying protocol parameters to be used.
    *
    * @param native_acceptor A native acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   basic_socket_acceptor(const executor_type& ex,
       const protocol_type& protocol, const native_handle_type& native_acceptor)
     : impl_(0, ex)
   {
     boost::system::error_code ec;
     impl_.get_service().assign(impl_.get_implementation(),
         protocol, native_acceptor, ec);
     boost::asio::detail::throw_error(ec, "assign");
   }
 
   /// Construct a basic_socket_acceptor on an existing native acceptor.
   /**
    * This constructor creates an acceptor object to hold an existing native
    * acceptor.
    *
    * @param context An execution context which provides the I/O executor that
    * the acceptor will use, by default, to dispatch handlers for any
    * asynchronous operations performed on the acceptor.
    *
    * @param protocol An object specifying protocol parameters to be used.
    *
    * @param native_acceptor A native acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   template <typename ExecutionContext>
   basic_socket_acceptor(ExecutionContext& context,
       const protocol_type& protocol, const native_handle_type& native_acceptor,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
     : impl_(0, 0, context)
   {
     boost::system::error_code ec;
     impl_.get_service().assign(impl_.get_implementation(),
         protocol, native_acceptor, ec);
     boost::asio::detail::throw_error(ec, "assign");
   }
 
   /// Move-construct a basic_socket_acceptor from another.
   /**
    * This constructor moves an acceptor from one object to another.
    *
    * @param other The other basic_socket_acceptor object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_socket_acceptor(const executor_type&)
    * constructor.
    */
   basic_socket_acceptor(basic_socket_acceptor&& other) noexcept
     : impl_(std::move(other.impl_))
   {
   }
 
   /// Move-assign a basic_socket_acceptor from another.
   /**
    * This assignment operator moves an acceptor from one object to another.
    *
    * @param other The other basic_socket_acceptor object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_socket_acceptor(const executor_type&)
    * constructor.
    */
   basic_socket_acceptor& operator=(basic_socket_acceptor&& other)
   {
     impl_ = std::move(other.impl_);
     return *this;
   }
 
   // All socket acceptors have access to each other's implementations.
   template <typename Protocol1, typename Executor1>
   friend class basic_socket_acceptor;
 
   /// Move-construct a basic_socket_acceptor from an acceptor of another
   /// protocol type.
   /**
    * This constructor moves an acceptor from one object to another.
    *
    * @param other The other basic_socket_acceptor object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_socket_acceptor(const executor_type&)
    * constructor.
    */
   template <typename Protocol1, typename Executor1>
   basic_socket_acceptor(basic_socket_acceptor<Protocol1, Executor1>&& other,
       constraint_t<
         is_convertible<Protocol1, Protocol>::value
           && is_convertible<Executor1, Executor>::value
       > = 0)
     : impl_(std::move(other.impl_))
   {
   }
 
   /// Move-assign a basic_socket_acceptor from an acceptor of another protocol
   /// type.
   /**
    * This assignment operator moves an acceptor from one object to another.
    *
    * @param other The other basic_socket_acceptor object from which the move
    * will occur.
    *
    * @note Following the move, the moved-from object is in the same state as if
    * constructed using the @c basic_socket_acceptor(const executor_type&)
    * constructor.
    */
   template <typename Protocol1, typename Executor1>
   constraint_t<
     is_convertible<Protocol1, Protocol>::value
       && is_convertible<Executor1, Executor>::value,
     basic_socket_acceptor&
   > operator=(basic_socket_acceptor<Protocol1, Executor1>&& other)
   {
     basic_socket_acceptor tmp(std::move(other));
     impl_ = std::move(tmp.impl_);
     return *this;
   }
 
   /// Destroys the acceptor.
   /**
    * This function destroys the acceptor, cancelling any outstanding
    * asynchronous operations associated with the acceptor as if by calling
    * @c cancel.
    */
   ~basic_socket_acceptor()
   {
   }
 
   /// Get the executor associated with the object.
   const executor_type& get_executor() noexcept
   {
     return impl_.get_executor();
   }
 
   /// Open the acceptor using the specified protocol.
   /**
    * This function opens the socket acceptor so that it will use the specified
    * protocol.
    *
    * @param protocol An object specifying which protocol is to be used.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * acceptor.open(boost::asio::ip::tcp::v4());
    * @endcode
    */
   void open(const protocol_type& protocol = protocol_type())
   {
     boost::system::error_code ec;
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     boost::asio::detail::throw_error(ec, "open");
   }
 
   /// Open the acceptor using the specified protocol.
   /**
    * This function opens the socket acceptor so that it will use the specified
    * protocol.
    *
    * @param protocol An object specifying which protocol is to be used.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * boost::system::error_code ec;
    * acceptor.open(boost::asio::ip::tcp::v4(), ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   BOOST_ASIO_SYNC_OP_VOID open(const protocol_type& protocol,
       boost::system::error_code& ec)
   {
     impl_.get_service().open(impl_.get_implementation(), protocol, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Assigns an existing native acceptor to the acceptor.
   /*
    * This function opens the acceptor to hold an existing native acceptor.
    *
    * @param protocol An object specifying which protocol is to be used.
    *
    * @param native_acceptor A native acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   void assign(const protocol_type& protocol,
       const native_handle_type& native_acceptor)
   {
     boost::system::error_code ec;
     impl_.get_service().assign(impl_.get_implementation(),
         protocol, native_acceptor, ec);
     boost::asio::detail::throw_error(ec, "assign");
   }
 
   /// Assigns an existing native acceptor to the acceptor.
   /*
    * This function opens the acceptor to hold an existing native acceptor.
    *
    * @param protocol An object specifying which protocol is to be used.
    *
    * @param native_acceptor A native acceptor.
    *
    * @param ec Set to indicate what error occurred, if any.
    */
   BOOST_ASIO_SYNC_OP_VOID assign(const protocol_type& protocol,
       const native_handle_type& native_acceptor, boost::system::error_code& ec)
   {
     impl_.get_service().assign(impl_.get_implementation(),
         protocol, native_acceptor, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Determine whether the acceptor is open.
   bool is_open() const
   {
     return impl_.get_service().is_open(impl_.get_implementation());
   }
 
   /// Bind the acceptor to the given local endpoint.
   /**
    * This function binds the socket acceptor to the specified endpoint on the
    * local machine.
    *
    * @param endpoint An endpoint on the local machine to which the socket
    * acceptor will be bound.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::tcp::v4(), 12345);
    * acceptor.open(endpoint.protocol());
    * acceptor.bind(endpoint);
    * @endcode
    */
   void bind(const endpoint_type& endpoint)
   {
     boost::system::error_code ec;
     impl_.get_service().bind(impl_.get_implementation(), endpoint, ec);
     boost::asio::detail::throw_error(ec, "bind");
   }
 
   /// Bind the acceptor to the given local endpoint.
   /**
    * This function binds the socket acceptor to the specified endpoint on the
    * local machine.
    *
    * @param endpoint An endpoint on the local machine to which the socket
    * acceptor will be bound.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::tcp::v4(), 12345);
    * acceptor.open(endpoint.protocol());
    * boost::system::error_code ec;
    * acceptor.bind(endpoint, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   BOOST_ASIO_SYNC_OP_VOID bind(const endpoint_type& endpoint,
       boost::system::error_code& ec)
   {
     impl_.get_service().bind(impl_.get_implementation(), endpoint, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Place the acceptor into the state where it will listen for new
   /// connections.
   /**
    * This function puts the socket acceptor into the state where it may accept
    * new connections.
    *
    * @param backlog The maximum length of the queue of pending connections.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   void listen(int backlog = socket_base::max_listen_connections)
   {
     boost::system::error_code ec;
     impl_.get_service().listen(impl_.get_implementation(), backlog, ec);
     boost::asio::detail::throw_error(ec, "listen");
   }
 
   /// Place the acceptor into the state where it will listen for new
   /// connections.
   /**
    * This function puts the socket acceptor into the state where it may accept
    * new connections.
    *
    * @param backlog The maximum length of the queue of pending connections.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::system::error_code ec;
    * acceptor.listen(boost::asio::socket_base::max_listen_connections, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   BOOST_ASIO_SYNC_OP_VOID listen(int backlog, boost::system::error_code& ec)
   {
     impl_.get_service().listen(impl_.get_implementation(), backlog, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Close the acceptor.
   /**
    * This function is used to close the acceptor. Any asynchronous accept
    * operations will be cancelled immediately.
    *
    * A subsequent call to open() is required before the acceptor can again be
    * used to again perform socket accept operations.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   void close()
   {
     boost::system::error_code ec;
     impl_.get_service().close(impl_.get_implementation(), ec);
     boost::asio::detail::throw_error(ec, "close");
   }
 
   /// Close the acceptor.
   /**
    * This function is used to close the acceptor. Any asynchronous accept
    * operations will be cancelled immediately.
    *
    * A subsequent call to open() is required before the acceptor can again be
    * used to again perform socket accept operations.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::system::error_code ec;
    * acceptor.close(ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   BOOST_ASIO_SYNC_OP_VOID close(boost::system::error_code& ec)
   {
     impl_.get_service().close(impl_.get_implementation(), ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Release ownership of the underlying native acceptor.
   /**
    * This function causes all outstanding asynchronous accept operations to
    * finish immediately, and the handlers for cancelled operations will be
    * passed the boost::asio::error::operation_aborted error. Ownership of the
    * native acceptor is then transferred to the caller.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @note This function is unsupported on Windows versions prior to Windows
    * 8.1, and will fail with boost::asio::error::operation_not_supported on
    * these platforms.
    */
 #if defined(BOOST_ASIO_MSVC) && (BOOST_ASIO_MSVC >= 1400) \
   && (!defined(_WIN32_WINNT) || _WIN32_WINNT < 0x0603)
   __declspec(deprecated("This function always fails with "
         "operation_not_supported when used on Windows versions "
         "prior to Windows 8.1."))
 #endif
   native_handle_type release()
   {
     boost::system::error_code ec;
     native_handle_type s = impl_.get_service().release(
         impl_.get_implementation(), ec);
     boost::asio::detail::throw_error(ec, "release");
     return s;
   }
 
   /// Release ownership of the underlying native acceptor.
   /**
    * This function causes all outstanding asynchronous accept operations to
    * finish immediately, and the handlers for cancelled operations will be
    * passed the boost::asio::error::operation_aborted error. Ownership of the
    * native acceptor is then transferred to the caller.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @note This function is unsupported on Windows versions prior to Windows
    * 8.1, and will fail with boost::asio::error::operation_not_supported on
    * these platforms.
    */
 #if defined(BOOST_ASIO_MSVC) && (BOOST_ASIO_MSVC >= 1400) \
   && (!defined(_WIN32_WINNT) || _WIN32_WINNT < 0x0603)
   __declspec(deprecated("This function always fails with "
         "operation_not_supported when used on Windows versions "
         "prior to Windows 8.1."))
 #endif
   native_handle_type release(boost::system::error_code& ec)
   {
     return impl_.get_service().release(impl_.get_implementation(), ec);
   }
 
   /// Get the native acceptor representation.
   /**
    * This function may be used to obtain the underlying representation of the
    * acceptor. This is intended to allow access to native acceptor functionality
    * that is not otherwise provided.
    */
   native_handle_type native_handle()
   {
     return impl_.get_service().native_handle(impl_.get_implementation());
   }
 
   /// Cancel all asynchronous operations associated with the acceptor.
   /**
    * This function causes all outstanding asynchronous connect, send and receive
    * operations to finish immediately, and the handlers for cancelled operations
    * will be passed the boost::asio::error::operation_aborted error.
    *
    * @throws boost::system::system_error Thrown on failure.
    */
   void cancel()
   {
     boost::system::error_code ec;
     impl_.get_service().cancel(impl_.get_implementation(), ec);
     boost::asio::detail::throw_error(ec, "cancel");
   }
 
   /// Cancel all asynchronous operations associated with the acceptor.
   /**
    * This function causes all outstanding asynchronous connect, send and receive
    * operations to finish immediately, and the handlers for cancelled operations
    * will be passed the boost::asio::error::operation_aborted error.
    *
    * @param ec Set to indicate what error occurred, if any.
    */
   BOOST_ASIO_SYNC_OP_VOID cancel(boost::system::error_code& ec)
   {
     impl_.get_service().cancel(impl_.get_implementation(), ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Set an option on the acceptor.
   /**
    * This function is used to set an option on the acceptor.
    *
    * @param option The new option value to be set on the acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @sa SettableSocketOption @n
    * boost::asio::socket_base::reuse_address
    * boost::asio::socket_base::enable_connection_aborted
    *
    * @par Example
    * Setting the SOL_SOCKET/SO_REUSEADDR option:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::reuse_address option(true);
    * acceptor.set_option(option);
    * @endcode
    */
   template <typename SettableSocketOption>
   void set_option(const SettableSocketOption& option)
   {
     boost::system::error_code ec;
     impl_.get_service().set_option(impl_.get_implementation(), option, ec);
     boost::asio::detail::throw_error(ec, "set_option");
   }
 
   /// Set an option on the acceptor.
   /**
    * This function is used to set an option on the acceptor.
    *
    * @param option The new option value to be set on the acceptor.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @sa SettableSocketOption @n
    * boost::asio::socket_base::reuse_address
    * boost::asio::socket_base::enable_connection_aborted
    *
    * @par Example
    * Setting the SOL_SOCKET/SO_REUSEADDR option:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::reuse_address option(true);
    * boost::system::error_code ec;
    * acceptor.set_option(option, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename SettableSocketOption>
   BOOST_ASIO_SYNC_OP_VOID set_option(const SettableSocketOption& option,
       boost::system::error_code& ec)
   {
     impl_.get_service().set_option(impl_.get_implementation(), option, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Get an option from the acceptor.
   /**
    * This function is used to get the current value of an option on the
    * acceptor.
    *
    * @param option The option value to be obtained from the acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @sa GettableSocketOption @n
    * boost::asio::socket_base::reuse_address
    *
    * @par Example
    * Getting the value of the SOL_SOCKET/SO_REUSEADDR option:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::reuse_address option;
    * acceptor.get_option(option);
    * bool is_set = option.get();
    * @endcode
    */
   template <typename GettableSocketOption>
   void get_option(GettableSocketOption& option) const
   {
     boost::system::error_code ec;
     impl_.get_service().get_option(impl_.get_implementation(), option, ec);
     boost::asio::detail::throw_error(ec, "get_option");
   }
 
   /// Get an option from the acceptor.
   /**
    * This function is used to get the current value of an option on the
    * acceptor.
    *
    * @param option The option value to be obtained from the acceptor.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @sa GettableSocketOption @n
    * boost::asio::socket_base::reuse_address
    *
    * @par Example
    * Getting the value of the SOL_SOCKET/SO_REUSEADDR option:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::reuse_address option;
    * boost::system::error_code ec;
    * acceptor.get_option(option, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * bool is_set = option.get();
    * @endcode
    */
   template <typename GettableSocketOption>
   BOOST_ASIO_SYNC_OP_VOID get_option(GettableSocketOption& option,
       boost::system::error_code& ec) const
   {
     impl_.get_service().get_option(impl_.get_implementation(), option, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Perform an IO control command on the acceptor.
   /**
    * This function is used to execute an IO control command on the acceptor.
    *
    * @param command The IO control command to be performed on the acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @sa IoControlCommand @n
    * boost::asio::socket_base::non_blocking_io
    *
    * @par Example
    * Getting the number of bytes ready to read:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::non_blocking_io command(true);
    * socket.io_control(command);
    * @endcode
    */
   template <typename IoControlCommand>
   void io_control(IoControlCommand& command)
   {
     boost::system::error_code ec;
     impl_.get_service().io_control(impl_.get_implementation(), command, ec);
     boost::asio::detail::throw_error(ec, "io_control");
   }
 
   /// Perform an IO control command on the acceptor.
   /**
    * This function is used to execute an IO control command on the acceptor.
    *
    * @param command The IO control command to be performed on the acceptor.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @sa IoControlCommand @n
    * boost::asio::socket_base::non_blocking_io
    *
    * @par Example
    * Getting the number of bytes ready to read:
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::acceptor::non_blocking_io command(true);
    * boost::system::error_code ec;
    * socket.io_control(command, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename IoControlCommand>
   BOOST_ASIO_SYNC_OP_VOID io_control(IoControlCommand& command,
       boost::system::error_code& ec)
   {
     impl_.get_service().io_control(impl_.get_implementation(), command, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Gets the non-blocking mode of the acceptor.
   /**
    * @returns @c true if the acceptor's synchronous operations will fail with
    * boost::asio::error::would_block if they are unable to perform the requested
    * operation immediately. If @c false, synchronous operations will block
    * until complete.
    *
    * @note The non-blocking mode has no effect on the behaviour of asynchronous
    * operations. Asynchronous operations will never fail with the error
    * boost::asio::error::would_block.
    */
   bool non_blocking() const
   {
     return impl_.get_service().non_blocking(impl_.get_implementation());
   }
 
   /// Sets the non-blocking mode of the acceptor.
   /**
    * @param mode If @c true, the acceptor's synchronous operations will fail
    * with boost::asio::error::would_block if they are unable to perform the
    * requested operation immediately. If @c false, synchronous operations will
    * block until complete.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @note The non-blocking mode has no effect on the behaviour of asynchronous
    * operations. Asynchronous operations will never fail with the error
    * boost::asio::error::would_block.
    */
   void non_blocking(bool mode)
   {
     boost::system::error_code ec;
     impl_.get_service().non_blocking(impl_.get_implementation(), mode, ec);
     boost::asio::detail::throw_error(ec, "non_blocking");
   }
 
   /// Sets the non-blocking mode of the acceptor.
   /**
    * @param mode If @c true, the acceptor's synchronous operations will fail
    * with boost::asio::error::would_block if they are unable to perform the
    * requested operation immediately. If @c false, synchronous operations will
    * block until complete.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @note The non-blocking mode has no effect on the behaviour of asynchronous
    * operations. Asynchronous operations will never fail with the error
    * boost::asio::error::would_block.
    */
   BOOST_ASIO_SYNC_OP_VOID non_blocking(
       bool mode, boost::system::error_code& ec)
   {
     impl_.get_service().non_blocking(impl_.get_implementation(), mode, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Gets the non-blocking mode of the native acceptor implementation.
   /**
    * This function is used to retrieve the non-blocking mode of the underlying
    * native acceptor. This mode has no effect on the behaviour of the acceptor
    * object's synchronous operations.
    *
    * @returns @c true if the underlying acceptor is in non-blocking mode and
    * direct system calls may fail with boost::asio::error::would_block (or the
    * equivalent system error).
    *
    * @note The current non-blocking mode is cached by the acceptor object.
    * Consequently, the return value may be incorrect if the non-blocking mode
    * was set directly on the native acceptor.
    */
   bool native_non_blocking() const
   {
     return impl_.get_service().native_non_blocking(impl_.get_implementation());
   }
 
   /// Sets the non-blocking mode of the native acceptor implementation.
   /**
    * This function is used to modify the non-blocking mode of the underlying
    * native acceptor. It has no effect on the behaviour of the acceptor object's
    * synchronous operations.
    *
    * @param mode If @c true, the underlying acceptor is put into non-blocking
    * mode and direct system calls may fail with boost::asio::error::would_block
    * (or the equivalent system error).
    *
    * @throws boost::system::system_error Thrown on failure. If the @c mode is
    * @c false, but the current value of @c non_blocking() is @c true, this
    * function fails with boost::asio::error::invalid_argument, as the
    * combination does not make sense.
    */
   void native_non_blocking(bool mode)
   {
     boost::system::error_code ec;
     impl_.get_service().native_non_blocking(
         impl_.get_implementation(), mode, ec);
     boost::asio::detail::throw_error(ec, "native_non_blocking");
   }
 
   /// Sets the non-blocking mode of the native acceptor implementation.
   /**
    * This function is used to modify the non-blocking mode of the underlying
    * native acceptor. It has no effect on the behaviour of the acceptor object's
    * synchronous operations.
    *
    * @param mode If @c true, the underlying acceptor is put into non-blocking
    * mode and direct system calls may fail with boost::asio::error::would_block
    * (or the equivalent system error).
    *
    * @param ec Set to indicate what error occurred, if any. If the @c mode is
    * @c false, but the current value of @c non_blocking() is @c true, this
    * function fails with boost::asio::error::invalid_argument, as the
    * combination does not make sense.
    */
   BOOST_ASIO_SYNC_OP_VOID native_non_blocking(
       bool mode, boost::system::error_code& ec)
   {
     impl_.get_service().native_non_blocking(
         impl_.get_implementation(), mode, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Get the local endpoint of the acceptor.
   /**
    * This function is used to obtain the locally bound endpoint of the acceptor.
    *
    * @returns An object that represents the local endpoint of the acceptor.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint = acceptor.local_endpoint();
    * @endcode
    */
   endpoint_type local_endpoint() const
   {
     boost::system::error_code ec;
     endpoint_type ep = impl_.get_service().local_endpoint(
         impl_.get_implementation(), ec);
     boost::asio::detail::throw_error(ec, "local_endpoint");
     return ep;
   }
 
   /// Get the local endpoint of the acceptor.
   /**
    * This function is used to obtain the locally bound endpoint of the acceptor.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns An object that represents the local endpoint of the acceptor.
    * Returns a default-constructed endpoint object if an error occurred and the
    * error handler did not throw an exception.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::system::error_code ec;
    * boost::asio::ip::tcp::endpoint endpoint = acceptor.local_endpoint(ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   endpoint_type local_endpoint(boost::system::error_code& ec) const
   {
     return impl_.get_service().local_endpoint(impl_.get_implementation(), ec);
   }
 
   /// Wait for the acceptor to become ready to read, ready to write, or to have
   /// pending error conditions.
   /**
    * This function is used to perform a blocking wait for an acceptor to enter
    * a ready to read, write or error condition state.
    *
    * @param w Specifies the desired acceptor state.
    *
    * @par Example
    * Waiting for an acceptor to become readable.
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * acceptor.wait(boost::asio::ip::tcp::acceptor::wait_read);
    * @endcode
    */
   void wait(wait_type w)
   {
     boost::system::error_code ec;
     impl_.get_service().wait(impl_.get_implementation(), w, ec);
     boost::asio::detail::throw_error(ec, "wait");
   }
 
   /// Wait for the acceptor to become ready to read, ready to write, or to have
   /// pending error conditions.
   /**
    * This function is used to perform a blocking wait for an acceptor to enter
    * a ready to read, write or error condition state.
    *
    * @param w Specifies the desired acceptor state.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * Waiting for an acceptor to become readable.
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::system::error_code ec;
    * acceptor.wait(boost::asio::ip::tcp::acceptor::wait_read, ec);
    * @endcode
    */
   BOOST_ASIO_SYNC_OP_VOID wait(wait_type w, boost::system::error_code& ec)
   {
     impl_.get_service().wait(impl_.get_implementation(), w, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Asynchronously wait for the acceptor to become ready to read, ready to
   /// write, or to have pending error conditions.
   /**
    * This function is used to perform an asynchronous wait for an acceptor to
    * enter a ready to read, write or error condition state. It is an initiating
    * function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * @param w Specifies the desired acceptor state.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the wait completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   const boost::system::error_code& error // Result of operation.
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code) @endcode
    *
    * @par Example
    * @code
    * void wait_handler(const boost::system::error_code& error)
    * {
    *   if (!error)
    *   {
    *     // Wait succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * acceptor.async_wait(
    *     boost::asio::ip::tcp::acceptor::wait_read,
    *     wait_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code))
         WaitToken = default_completion_token_t<executor_type>>
   auto async_wait(wait_type w,
       WaitToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<WaitToken, void (boost::system::error_code)>(
         declval<initiate_async_wait>(), token, w))
   {
     return async_initiate<WaitToken, void (boost::system::error_code)>(
         initiate_async_wait(this), token, w);
   }
 
 #if !defined(BOOST_ASIO_NO_EXTENSIONS)
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer into the
    * given socket. The function call will block until a new connection has been
    * accepted successfully or an error occurs.
    *
    * @param peer The socket into which the new connection will be accepted.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(my_context);
    * acceptor.accept(socket);
    * @endcode
    */
   template <typename Protocol1, typename Executor1>
   void accept(basic_socket<Protocol1, Executor1>& peer,
       constraint_t<
         is_convertible<Protocol, Protocol1>::value
       > = 0)
   {
     boost::system::error_code ec;
     impl_.get_service().accept(impl_.get_implementation(),
         peer, static_cast<endpoint_type*>(0), ec);
     boost::asio::detail::throw_error(ec, "accept");
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer into the
    * given socket. The function call will block until a new connection has been
    * accepted successfully or an error occurs.
    *
    * @param peer The socket into which the new connection will be accepted.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(my_context);
    * boost::system::error_code ec;
    * acceptor.accept(socket, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename Protocol1, typename Executor1>
   BOOST_ASIO_SYNC_OP_VOID accept(
       basic_socket<Protocol1, Executor1>& peer, boost::system::error_code& ec,
       constraint_t<
         is_convertible<Protocol, Protocol1>::value
       > = 0)
   {
     impl_.get_service().accept(impl_.get_implementation(),
         peer, static_cast<endpoint_type*>(0), ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection into a
    * socket, and additionally obtain the endpoint of the remote peer. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * @param peer The socket into which the new connection will be accepted.
    * Ownership of the peer object is retained by the caller, which must
    * guarantee that it is valid until the completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   const boost::system::error_code& error // Result of operation.
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(my_context);
    * acceptor.async_accept(socket, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename Protocol1, typename Executor1,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code))
         AcceptToken = default_completion_token_t<executor_type>>
   auto async_accept(basic_socket<Protocol1, Executor1>& peer,
       AcceptToken&& token = default_completion_token_t<executor_type>(),
       constraint_t<
         is_convertible<Protocol, Protocol1>::value
       > = 0)
     -> decltype(
       async_initiate<AcceptToken, void (boost::system::error_code)>(
         declval<initiate_async_accept>(), token,
         &peer, static_cast<endpoint_type*>(0)))
   {
     return async_initiate<AcceptToken, void (boost::system::error_code)>(
         initiate_async_accept(this), token,
         &peer, static_cast<endpoint_type*>(0));
   }
 
   /// Accept a new connection and obtain the endpoint of the peer
   /**
    * This function is used to accept a new connection from a peer into the
    * given socket, and additionally provide the endpoint of the remote peer.
    * The function call will block until a new connection has been accepted
    * successfully or an error occurs.
    *
    * @param peer The socket into which the new connection will be accepted.
    *
    * @param peer_endpoint An endpoint object which will receive the endpoint of
    * the remote peer.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(my_context);
    * boost::asio::ip::tcp::endpoint endpoint;
    * acceptor.accept(socket, endpoint);
    * @endcode
    */
   template <typename Executor1>
   void accept(basic_socket<protocol_type, Executor1>& peer,
       endpoint_type& peer_endpoint)
   {
     boost::system::error_code ec;
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     boost::asio::detail::throw_error(ec, "accept");
   }
 
   /// Accept a new connection and obtain the endpoint of the peer
   /**
    * This function is used to accept a new connection from a peer into the
    * given socket, and additionally provide the endpoint of the remote peer.
    * The function call will block until a new connection has been accepted
    * successfully or an error occurs.
    *
    * @param peer The socket into which the new connection will be accepted.
    *
    * @param peer_endpoint An endpoint object which will receive the endpoint of
    * the remote peer.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(my_context);
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::system::error_code ec;
    * acceptor.accept(socket, endpoint, ec);
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename Executor1>
   BOOST_ASIO_SYNC_OP_VOID accept(basic_socket<protocol_type, Executor1>& peer,
       endpoint_type& peer_endpoint, boost::system::error_code& ec)
   {
     impl_.get_service().accept(
         impl_.get_implementation(), peer, &peer_endpoint, ec);
     BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection into a
    * socket, and additionally obtain the endpoint of the remote peer. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * @param peer The socket into which the new connection will be accepted.
    * Ownership of the peer object is retained by the caller, which must
    * guarantee that it is valid until the completion handler is called.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written. Ownership of the peer_endpoint object is
    * retained by the caller, which must guarantee that it is valid until the
    * handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   const boost::system::error_code& error // Result of operation.
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code) @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename Executor1,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code))
         AcceptToken = default_completion_token_t<executor_type>>
   auto async_accept(basic_socket<protocol_type, Executor1>& peer,
       endpoint_type& peer_endpoint,
       AcceptToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<AcceptToken, void (boost::system::error_code)>(
         declval<initiate_async_accept>(), token, &peer, &peer_endpoint))
   {
     return async_initiate<AcceptToken, void (boost::system::error_code)>(
         initiate_async_accept(this), token, &peer, &peer_endpoint);
   }
 #endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept());
    * @endcode
    */
   typename Protocol::socket::template rebind_executor<executor_type>::other
   accept()
   {
     boost::system::error_code ec;
     typename Protocol::socket::template rebind_executor<
       executor_type>::other peer(impl_.get_executor());
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept(ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   typename Protocol::socket::template rebind_executor<executor_type>::other
   accept(boost::system::error_code& ec)
   {
     typename Protocol::socket::template rebind_executor<
       executor_type>::other peer(impl_.get_executor());
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     return peer;
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template
    *     rebind_executor<executor_type>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template
    *      rebind_executor<executor_type>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * acceptor.async_accept(accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           executor_type>::other)) MoveAcceptToken
             = default_completion_token_t<executor_type>>
   auto async_accept(
       MoveAcceptToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code, typename Protocol::socket::template
           rebind_executor<executor_type>::other)>(
             declval<initiate_async_move_accept>(), token,
             declval<const executor_type&>(), static_cast<endpoint_type*>(0),
             static_cast<typename Protocol::socket::template
               rebind_executor<executor_type>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code, typename Protocol::socket::template
         rebind_executor<executor_type>::other)>(
           initiate_async_move_accept(this), token,
           impl_.get_executor(), static_cast<endpoint_type*>(0),
           static_cast<typename Protocol::socket::template
             rebind_executor<executor_type>::other*>(0));
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly
    * accepted socket.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept());
    * @endcode
    */
   template <typename Executor1>
   typename Protocol::socket::template rebind_executor<Executor1>::other
   accept(const Executor1& ex,
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
   {
     boost::system::error_code ec;
     typename Protocol::socket::template
       rebind_executor<Executor1>::other peer(ex);
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept());
    * @endcode
    */
   template <typename ExecutionContext>
   typename Protocol::socket::template rebind_executor<
       typename ExecutionContext::executor_type>::other
   accept(ExecutionContext& context,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
   {
     boost::system::error_code ec;
     typename Protocol::socket::template rebind_executor<
         typename ExecutionContext::executor_type>::other peer(context);
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly accepted
    * socket.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept(my_context2, ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename Executor1>
   typename Protocol::socket::template rebind_executor<Executor1>::other
   accept(const Executor1& ex, boost::system::error_code& ec,
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
   {
     typename Protocol::socket::template
       rebind_executor<Executor1>::other peer(ex);
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::socket socket(acceptor.accept(my_context2, ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename ExecutionContext>
   typename Protocol::socket::template rebind_executor<
       typename ExecutionContext::executor_type>::other
   accept(ExecutionContext& context, boost::system::error_code& ec,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
   {
     typename Protocol::socket::template rebind_executor<
         typename ExecutionContext::executor_type>::other peer(context);
     impl_.get_service().accept(impl_.get_implementation(), peer, 0, ec);
     return peer;
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly accepted
    * socket.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template rebind_executor<
    *     Executor1>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template rebind_executor<
    *      Executor1>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * acceptor.async_accept(my_context2, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename Executor1,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           constraint_t<is_executor<Executor1>::value
             || execution::is_executor<Executor1>::value,
               Executor1>>::other)) MoveAcceptToken
                 = default_completion_token_t<executor_type>>
   auto async_accept(const Executor1& ex,
       MoveAcceptToken&& token = default_completion_token_t<executor_type>(),
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code,
           typename Protocol::socket::template rebind_executor<
             Executor1>::other)>(
               declval<initiate_async_move_accept>(), token,
               ex, static_cast<endpoint_type*>(0),
               static_cast<typename Protocol::socket::template
                 rebind_executor<Executor1>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           Executor1>::other)>(
             initiate_async_move_accept(this), token,
             ex, static_cast<endpoint_type*>(0),
             static_cast<typename Protocol::socket::template
               rebind_executor<Executor1>::other*>(0));
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template rebind_executor<
    *     typename ExecutionContext::executor_type>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template rebind_executor<
    *      typename ExecutionContext::executor_type>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * acceptor.async_accept(my_context2, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename ExecutionContext,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           typename ExecutionContext::executor_type>::other)) MoveAcceptToken
             = default_completion_token_t<executor_type>>
   auto async_accept(ExecutionContext& context,
       MoveAcceptToken&& token = default_completion_token_t<executor_type>(),
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code,
           typename Protocol::socket::template rebind_executor<
             typename ExecutionContext::executor_type>::other)>(
               declval<initiate_async_move_accept>(), token,
               context.get_executor(), static_cast<endpoint_type*>(0),
               static_cast<typename Protocol::socket::template rebind_executor<
                 typename ExecutionContext::executor_type>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           typename ExecutionContext::executor_type>::other)>(
             initiate_async_move_accept(this), token,
             context.get_executor(), static_cast<endpoint_type*>(0),
             static_cast<typename Protocol::socket::template rebind_executor<
               typename ExecutionContext::executor_type>::other*>(0));
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(acceptor.accept(endpoint));
    * @endcode
    */
   typename Protocol::socket::template rebind_executor<executor_type>::other
   accept(endpoint_type& peer_endpoint)
   {
     boost::system::error_code ec;
     typename Protocol::socket::template rebind_executor<
       executor_type>::other peer(impl_.get_executor());
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(acceptor.accept(endpoint, ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   typename Protocol::socket::template rebind_executor<executor_type>::other
   accept(endpoint_type& peer_endpoint, boost::system::error_code& ec)
   {
     typename Protocol::socket::template rebind_executor<
       executor_type>::other peer(impl_.get_executor());
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     return peer;
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written. Ownership of the peer_endpoint object is
    * retained by the caller, which must guarantee that it is valid until the
    * completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template
    *     rebind_executor<executor_type>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template
    *      rebind_executor<executor_type>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * acceptor.async_accept(endpoint, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           executor_type>::other)) MoveAcceptToken
             = default_completion_token_t<executor_type>>
   auto async_accept(endpoint_type& peer_endpoint,
       MoveAcceptToken&& token = default_completion_token_t<executor_type>())
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code, typename Protocol::socket::template
           rebind_executor<executor_type>::other)>(
             declval<initiate_async_move_accept>(), token,
             declval<const executor_type&>(), &peer_endpoint,
             static_cast<typename Protocol::socket::template
               rebind_executor<executor_type>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code, typename Protocol::socket::template
         rebind_executor<executor_type>::other)>(
           initiate_async_move_accept(this), token,
           impl_.get_executor(), &peer_endpoint,
           static_cast<typename Protocol::socket::template
             rebind_executor<executor_type>::other*>(0));
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly accepted
    * socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(
    *     acceptor.accept(my_context2, endpoint));
    * @endcode
    */
   template <typename Executor1>
   typename Protocol::socket::template rebind_executor<Executor1>::other
   accept(const Executor1& ex, endpoint_type& peer_endpoint,
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
   {
     boost::system::error_code ec;
     typename Protocol::socket::template
         rebind_executor<Executor1>::other peer(ex);
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @returns A socket object representing the newly accepted connection.
    *
    * @throws boost::system::system_error Thrown on failure.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(
    *     acceptor.accept(my_context2, endpoint));
    * @endcode
    */
   template <typename ExecutionContext>
   typename Protocol::socket::template rebind_executor<
       typename ExecutionContext::executor_type>::other
   accept(ExecutionContext& context, endpoint_type& peer_endpoint,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
   {
     boost::system::error_code ec;
     typename Protocol::socket::template rebind_executor<
         typename ExecutionContext::executor_type>::other peer(context);
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     boost::asio::detail::throw_error(ec, "accept");
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly accepted
    * socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(
    *     acceptor.accept(my_context2, endpoint, ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename Executor1>
   typename Protocol::socket::template rebind_executor<Executor1>::other
   accept(const executor_type& ex,
       endpoint_type& peer_endpoint, boost::system::error_code& ec,
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
   {
     typename Protocol::socket::template
       rebind_executor<Executor1>::other peer(ex);
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     return peer;
   }
 
   /// Accept a new connection.
   /**
    * This function is used to accept a new connection from a peer. The function
    * call will block until a new connection has been accepted successfully or
    * an error occurs.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written.
    *
    * @param ec Set to indicate what error occurred, if any.
    *
    * @returns On success, a socket object representing the newly accepted
    * connection. On error, a socket object where is_open() is false.
    *
    * @par Example
    * @code
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * boost::asio::ip::tcp::socket socket(
    *     acceptor.accept(my_context2, endpoint, ec));
    * if (ec)
    * {
    *   // An error occurred.
    * }
    * @endcode
    */
   template <typename ExecutionContext>
   typename Protocol::socket::template rebind_executor<
       typename ExecutionContext::executor_type>::other
   accept(ExecutionContext& context,
       endpoint_type& peer_endpoint, boost::system::error_code& ec,
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
   {
     typename Protocol::socket::template rebind_executor<
         typename ExecutionContext::executor_type>::other peer(context);
     impl_.get_service().accept(impl_.get_implementation(),
         peer, &peer_endpoint, ec);
     return peer;
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param ex The I/O executor object to be used for the newly accepted
    * socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written. Ownership of the peer_endpoint object is
    * retained by the caller, which must guarantee that it is valid until the
    * completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template rebind_executor<
    *     Executor1>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template rebind_executor<
    *      Executor1>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * acceptor.async_accept(my_context2, endpoint, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename Executor1,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           constraint_t<is_executor<Executor1>::value
             || execution::is_executor<Executor1>::value,
               Executor1>>::other)) MoveAcceptToken
                 = default_completion_token_t<executor_type>>
   auto async_accept(const Executor1& ex, endpoint_type& peer_endpoint,
       MoveAcceptToken&& token = default_completion_token_t<executor_type>(),
       constraint_t<
         is_executor<Executor1>::value
           || execution::is_executor<Executor1>::value
       > = 0)
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code,
           typename Protocol::socket::template rebind_executor<
             Executor1>::other)>(
           declval<initiate_async_move_accept>(), token, ex, &peer_endpoint,
           static_cast<typename Protocol::socket::template
             rebind_executor<Executor1>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           Executor1>::other)>(
             initiate_async_move_accept(this), token, ex, &peer_endpoint,
             static_cast<typename Protocol::socket::template
               rebind_executor<Executor1>::other*>(0));
   }
 
   /// Start an asynchronous accept.
   /**
    * This function is used to asynchronously accept a new connection. It is an
    * initiating function for an @ref asynchronous_operation, and always returns
    * immediately.
    *
    * This overload requires that the Protocol template parameter satisfy the
    * AcceptableProtocol type requirements.
    *
    * @param context The I/O execution context object to be used for the newly
    * accepted socket.
    *
    * @param peer_endpoint An endpoint object into which the endpoint of the
    * remote peer will be written. Ownership of the peer_endpoint object is
    * retained by the caller, which must guarantee that it is valid until the
    * completion handler is called.
    *
    * @param token The @ref completion_token that will be used to produce a
    * completion handler, which will be called when the accept completes.
    * Potential completion tokens include @ref use_future, @ref use_awaitable,
    * @ref yield_context, or a function object with the correct completion
    * signature. The function signature of the completion handler must be:
    * @code void handler(
    *   // Result of operation.
    *   const boost::system::error_code& error,
    *
    *   // On success, the newly accepted socket.
    *   typename Protocol::socket::template rebind_executor<
    *     typename ExecutionContext::executor_type>::other peer
    * ); @endcode
    * Regardless of whether the asynchronous operation completes immediately or
    * not, the completion handler will not be invoked from within this function.
    * On immediate completion, invocation of the handler will be performed in a
    * manner equivalent to using boost::asio::post().
    *
    * @par Completion Signature
    * @code void(boost::system::error_code,
    *    typename Protocol::socket::template rebind_executor<
    *      typename ExecutionContext::executor_type>::other)) @endcode
    *
    * @par Example
    * @code
    * void accept_handler(const boost::system::error_code& error,
    *     boost::asio::ip::tcp::socket peer)
    * {
    *   if (!error)
    *   {
    *     // Accept succeeded.
    *   }
    * }
    *
    * ...
    *
    * boost::asio::ip::tcp::acceptor acceptor(my_context);
    * ...
    * boost::asio::ip::tcp::endpoint endpoint;
    * acceptor.async_accept(my_context2, endpoint, accept_handler);
    * @endcode
    *
    * @par Per-Operation Cancellation
    * On POSIX or Windows operating systems, this asynchronous operation supports
    * cancellation for the following boost::asio::cancellation_type values:
    *
    * @li @c cancellation_type::terminal
    *
    * @li @c cancellation_type::partial
    *
    * @li @c cancellation_type::total
    */
   template <typename ExecutionContext,
       BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           typename ExecutionContext::executor_type>::other)) MoveAcceptToken
             = default_completion_token_t<executor_type>>
   auto async_accept(ExecutionContext& context, endpoint_type& peer_endpoint,
       MoveAcceptToken&& token = default_completion_token_t<executor_type>(),
       constraint_t<
         is_convertible<ExecutionContext&, execution_context&>::value
       > = 0)
     -> decltype(
       async_initiate<MoveAcceptToken,
         void (boost::system::error_code,
           typename Protocol::socket::template rebind_executor<
             typename ExecutionContext::executor_type>::other)>(
               declval<initiate_async_move_accept>(), token,
               context.get_executor(), &peer_endpoint,
               static_cast<typename Protocol::socket::template rebind_executor<
                 typename ExecutionContext::executor_type>::other*>(0)))
   {
     return async_initiate<MoveAcceptToken,
       void (boost::system::error_code,
         typename Protocol::socket::template rebind_executor<
           typename ExecutionContext::executor_type>::other)>(
             initiate_async_move_accept(this), token,
             context.get_executor(), &peer_endpoint,
             static_cast<typename Protocol::socket::template rebind_executor<
               typename ExecutionContext::executor_type>::other*>(0));
   }
 
 private:
   // Disallow copying and assignment.
   basic_socket_acceptor(const basic_socket_acceptor&) = delete;
   basic_socket_acceptor& operator=(
       const basic_socket_acceptor&) = delete;
 
   class initiate_async_wait
   {
   public:
     typedef Executor executor_type;
 
     explicit initiate_async_wait(basic_socket_acceptor* self)
       : self_(self)
     {
     }
 
     const executor_type& get_executor() const noexcept
     {
       return self_->get_executor();
     }
 
     template <typename WaitHandler>
     void operator()(WaitHandler&& handler, wait_type w) const
     {
       // If you get an error on the following line it means that your handler
       // does not meet the documented type requirements for a WaitHandler.
       BOOST_ASIO_WAIT_HANDLER_CHECK(WaitHandler, handler) type_check;
 
       detail::non_const_lvalue<WaitHandler> handler2(handler);
       self_->impl_.get_service().async_wait(
           self_->impl_.get_implementation(), w,
           handler2.value, self_->impl_.get_executor());
     }
 
   private:
     basic_socket_acceptor* self_;
   };
 
   class initiate_async_accept
   {
   public:
     typedef Executor executor_type;
 
     explicit initiate_async_accept(basic_socket_acceptor* self)
       : self_(self)
     {
     }
 
     const executor_type& get_executor() const noexcept
     {
       return self_->get_executor();
     }
 
     template <typename AcceptHandler, typename Protocol1, typename Executor1>
     void operator()(AcceptHandler&& handler,
         basic_socket<Protocol1, Executor1>* peer,
         endpoint_type* peer_endpoint) const
     {
       // If you get an error on the following line it means that your handler
       // does not meet the documented type requirements for a AcceptHandler.
       BOOST_ASIO_ACCEPT_HANDLER_CHECK(AcceptHandler, handler) type_check;
 
       detail::non_const_lvalue<AcceptHandler> handler2(handler);
       self_->impl_.get_service().async_accept(
           self_->impl_.get_implementation(), *peer, peer_endpoint,
           handler2.value, self_->impl_.get_executor());
     }
 
   private:
     basic_socket_acceptor* self_;
   };
 
   class initiate_async_move_accept
   {
   public:
     typedef Executor executor_type;
 
     explicit initiate_async_move_accept(basic_socket_acceptor* self)
       : self_(self)
     {
     }
 
     const executor_type& get_executor() const noexcept
     {
       return self_->get_executor();
     }
 
     template <typename MoveAcceptHandler, typename Executor1, typename Socket>
     void operator()(MoveAcceptHandler&& handler,
         const Executor1& peer_ex, endpoint_type* peer_endpoint, Socket*) const
     {
       // If you get an error on the following line it means that your handler
       // does not meet the documented type requirements for a MoveAcceptHandler.
       BOOST_ASIO_MOVE_ACCEPT_HANDLER_CHECK(
           MoveAcceptHandler, handler, Socket) type_check;
 
       detail::non_const_lvalue<MoveAcceptHandler> handler2(handler);
       self_->impl_.get_service().async_move_accept(
           self_->impl_.get_implementation(), peer_ex, peer_endpoint,
           handler2.value, self_->impl_.get_executor());
     }
 
   private:
     basic_socket_acceptor* self_;
   };
 
 #if defined(BOOST_ASIO_WINDOWS_RUNTIME)
   detail::io_object_impl<
     detail::null_socket_service<Protocol>, Executor> impl_;
 #elif defined(BOOST_ASIO_HAS_IOCP)
   detail::io_object_impl<
     detail::win_iocp_socket_service<Protocol>, Executor> impl_;
 #elif defined(BOOST_ASIO_HAS_IO_URING_AS_DEFAULT)
   detail::io_object_impl<
     detail::io_uring_socket_service<Protocol>, Executor> impl_;
 #else
   detail::io_object_impl<
     detail::reactive_socket_service<Protocol>, Executor> impl_;
 #endif
 };
 
 } // namespace asio
 } // namespace boost
 
 #include <boost/asio/detail/pop_options.hpp>
 
 #endif // BOOST_ASIO_BASIC_SOCKET_ACCEPTOR_HPP

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