Networking TS compatibility

Asio now provides the interfaces and functionality specified by the "C++ Extensions for Networking" Technical Specification. In addition to access via the usual Asio header files, this functionality may be accessed through special headers that correspond to the header files defined in the TS. These are listed in the table below:

Networking TS header	Asio header
`#include <buffer>`	`#include <asio/ts/buffer.hpp>`
`#include <executor>`	`#include <asio/ts/executor.hpp>`
`#include <internet>`	`#include <asio/ts/internet.hpp>`
`#include <io_context>`	`#include <asio/ts/io_context.hpp>`
`#include <net>`	`#include <asio/ts/net.hpp>`
`#include <netfwd>`	`#include <asio/ts/netfwd.hpp>`
`#include <socket>`	`#include <asio/ts/socket.hpp>`
`#include <timer>`	`#include <asio/ts/timer.hpp>`

In some cases the new Networking TS compatible interfaces supersede older Asio facilities. In these cases the older interfaces have been deprecated. The table below shows the new Networking TS interfaces and the facilities they replace:

New interface	Old interface	Notes
`io_context`	`io_service`	The name `io_service` is retained as a typedef.
`dispatch`	`io_service::dispatch`	The `dispatch` free function can be used to submit functions to any Executor or ExecutionContext.
`post`	`io_service::post`	The `dispatch` free function can be used to submit functions to any Executor or ExecutionContext.
`defer`	`io_service::post` when the `asio_handler_is_continuation` hook returns true	The `defer` free function can be used to submit functions to any Executor or ExecutionContext.
`io_context::poll`	`io_service::poll` overload that takes `error_code&`	The `error_code` overload is not required.
`io_context::poll_one`	`io_service::poll_one` overload that takes `error_code&`	The `error_code` overload is not required.
`io_context::run`	`io_service::run` overload that takes `error_code&`	The `error_code` overload is not required.
`io_context::run_one`	`io_service::run_one` overload that takes `error_code&`	The `error_code` overload is not required.
`io_context::run_for`, `io_context::run_until`, `io_context::run_one_for`, and `io_context::run_one_until`		These functions add the ability to run an `io_context` for a limited time.
`io_context::restart`	`io_service::reset`
`io_context` constructor `concurrency_hint` parameter is type `int`	`io_context` constructor `concurrency_hint` parameter is type `std::size_t`	The old constructor has not been retained as a deprecated overload.
`execution_context`, `execution_context::service`, and `execution_context::id`	`io_service`, `io_service::service`, and `io_service::id`	The service-related functionality has been moved to the `execution_context` base class. This may also be used as a base for creating custom execution contexts.
`make_service`	`add_service`
`strand`	`io_service::strand`	This template works with any valid executor, and is itself a valid executor.
`executor_work_guard` and `make_work_guard`	`io_service::work`	Work tracking is now covered by the Executor requirements. These templates work with any valid executor.
`executor_binder` and `bind_executor`	`io_service::wrap` and `io_service::strand::wrap`	These templates work with any valid executor.
`async_result` with `CompletionToken` and `Signature` template parameters	`handler_type` and single parameter `async_result`	The `async_result` trait is now the single point of customisation for asynchronous operation completion handlers and return type.
`associated_executor` and `get_associated_executor`	`asio_handler_invoke`	The handler invocation hook has been replaced by the new Executor requirements and the associated executor traits.
`associated_allocator` and `get_associated_allocator`	`asio_handler_allocate` and `asio_handler_deallocate`	The handler allocation hooks have been replaced by the standard Allocator requirements and the associated allocator traits.
`const_buffer::data` and `mutable_buffer::data`	`buffer_cast`
`const_buffer::size` and `mutable_buffer::size`	`buffer_size` for single buffers	`buffer_size` is not deprecated for single buffers as `const_buffer` and `mutable_buffer` now satisfy the buffer sequence requirements
`const_buffer`	`const_buffers_1`	The ConstBufferSequence requirements have been modified such that `const_buffer` now satisfies them.
`mutable_buffer`	`mutable_buffers_1`	The MutableBufferSequence requirements have been modified such that `mutable_buffer` now satisfies them.
`basic_socket::get_executor` (and corresponding member for I/O objects such as timers, serial ports, etc.)	`basic_io_object::get_io_service`	Use `get_executor().context()` to obtain the associated `io_context`.
`socket_base::max_listen_connections`	`socket_base::max_connections`
`socket_base::wait_type`, `basic_socket::wait`, `basic_socket::async_wait`, `basic_socket_acceptor::wait`, and `basic_socket_acceptor::async_wait`	`null_buffers`	Operations for reactive I/O.
`basic_socket_acceptor::accept` returns a socket	`basic_socket_acceptor::accept` takes a socket by reference	Uses move support so requires C++11 or later. To accept a connection into a socket object on a different `io_context`, pass the destination context to `accept`.
`basic_socket_acceptor::async_accept` passes socket to handler	`basic_socket_acceptor::async_accept` takes a socket by reference	Uses move support so requires C++11 or later. To accept a connection into a socket object on a different `io_context`, pass the destination context to `async_accept`.
`connect` overloads that take a range	`connect` overloads that take a single iterator	The `ip::basic_resolver::resolve` function now returns a range. When the `resolve` function's result is passed directly to `connect`, the range overload will be selected.
`async_connect` overloads that take a range	`async_connect` overloads that take a single iterator	The `ip::basic_resolver::resolve` function now returns a range. When the `resolve` function's result is passed directly to `async_connect`, the range overload will be selected.
`basic_socket_streambuf::duration`	`basic_socket_streambuf::duration_type`
`basic_socket_streambuf::time_point`	`basic_socket_streambuf::time_type`
`basic_socket_streambuf::expiry`	`basic_socket_streambuf::expires_at` and `basic_socket_streambuf::expires_from_now` getters
`basic_socket_streambuf::expires_after`	`basic_socket_streambuf::expires_from_now` setter
`basic_socket_streambuf::error`	`basic_socket_streambuf::puberror`
`basic_socket_iostream::duration`	`basic_socket_iostream::duration_type`
`basic_socket_iostream::time_point`	`basic_socket_iostream::time_type`
`basic_socket_iostream::expiry`	`basic_socket_iostream::expires_at` and `basic_socket_iostream::expires_from_now` getters
`basic_socket_iostream::expires_after`	`basic_socket_iostream::expires_from_now` setter
`basic_waitable_timer::cancel`	`basic_waitable_timer::cancel` overload that takes `error_code&`	The `error_code` overload is not required.
`basic_waitable_timer::cancel_one`	`basic_waitable_timer::cancel_one` overload that takes `error_code&`	The `error_code` overload is not required.
`basic_waitable_timer::expires_at` setter	`basic_waitable_timer::expires_at` setter that takes `error_code&`	The `error_code` overload is not required.
`basic_waitable_timer::expiry`	`basic_waitable_timer::expires_at` and `basic_waitable_timer::expires_from_now` getters
`basic_waitable_timer::expires_after`	`basic_waitable_timer::expires_from_now` setter
`ip::make_address`	`ip::address::from_string`
`ip::make_address_v4`	`ip::address_v4::from_string` and `ip::address_v6::to_v4`
`ip::make_address_v6`	`ip::address_v6::from_string` and `ip::address_v6::v4_mapped`
`ip::address::to_string`	`ip::address::to_string` that takes `error_code&`	The `error_code` overload is not required.
`ip::address_v4::to_string`	`ip::address_v4::to_string` that takes `error_code&`	The `error_code` overload is not required.
`ip::address_v6::to_string`	`ip::address_v6::to_string` that takes `error_code&`	The `error_code` overload is not required.
No replacement	`ip::address_v6::is_v4_compatible` and `ip::address_v6::v4_compatible`
`ip::network_v4`	`ip::address_v4::broadcast`, `ip::address_v4::is_class_a`, `ip::address_v4::is_class_b`, `ip::address_v4::is_class_c`, and `ip::address_v4::netmask`	The `network_v4` class adds the ability to manipulate IPv4 network addresses using CIDR notation.
`ip::network_v6`		The `network_v6` class adds the ability to manipulate IPv6 network addresses using CIDR notation.
`ip::address_v4_iterator` and `ip::address_v4_range`		The `ip::address_v4_iterator` and `address_v4_range` classes add the ability to iterate over all, or a subset of, IPv4 addresses.
`ip::address_v6_iterator` and `ip::address_v6_range`		The `ip::address_v6_iterator` and `address_v6_range` classes add the ability to iterate over all, or a subset of, IPv6 addresses.
`ip::basic_resolver::results_type`	`ip::basic_resolver::iterator`	Resolvers now produce ranges rather than single iterators.
`ip::basic_resolver::resolve` overloads taking hostname and service as arguments	`ip::basic_resolver::resolve` overloads taking a `ip::basic_resolver::query`
`ip::basic_resolver::resolve` returns a range	`ip::basic_resolver::resolve` returns a single iterator
`ip::basic_resolver::async_resolve` overloads taking hostname and service as arguments	`ip::basic_resolver::async_resolve` overloads taking a `ip::basic_resolver::query`
`ip::basic_resolver::async_resolve` calls the handler with a range	`ip::basic_resolver::async_resolve` calls the handler with a single iterator