[/
 / Copyright (c) 2003-2020 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)
 /]

[section:using Using Asio]

[heading Supported Platforms]

The following platform and compiler combinations are regularly tested:

* Linux using g++ 4.1 or later
* Linux using clang 3.2 or later
* FreeBSD using g++ 4.1 or later
* macOS using Xcode 8 or later
* Win32 using Visual C++ 9.0 or later
* Win32 using g++ 4.1 or later (MinGW)
* Win64 using Visual C++ 9.0 or later

The following platforms may also work:

* AIX
* Android
* HP-UX
* iOS
* NetBSD
* OpenBSD
* QNX Neutrino
* Solaris
* Tru64
* Win32 using Cygwin. (`__USE_W32_SOCKETS` must be defined.)

[heading Dependencies]

The following libraries must be available in order to link programs that use
Asio:

* Boost.Coroutine (optional) if you use [link asio.reference.spawn
`spawn()`] to launch coroutines.

* Boost.Regex (optional) if you use any of the [link
asio.reference.read_until `read_until()`] or [link
asio.reference.async_read_until `async_read_until()`] overloads that take
a `boost::regex` parameter.

* [@http://www.openssl.org OpenSSL] (optional) if you use Asio's SSL
support.

Furthermore, some of the examples also require Boost.Date_Time or
Boost.Serialization libraries.

[note With MSVC or Borland C++ you may want to add `-DBOOST_DATE_TIME_NO_LIB`
and `-DBOOST_REGEX_NO_LIB` to your project settings to disable autolinking of
the Boost.Date_Time and Boost.Regex libraries respectively. Alternatively, you
may choose to build these libraries and link to them.]

[heading Optional separate compilation]

By default, Asio is a header-only library. However, some developers may prefer
to build Asio using separately compiled source code. To do this, add `#include
<asio/impl/src.hpp>` to one (and only one) source file in a program, then build
the program with `ASIO_SEPARATE_COMPILATION` defined in the project\/compiler
settings. Alternatively, `ASIO_DYN_LINK` may be defined to build a
separately-compiled Asio as part of a shared library.

If using Asio's SSL support, you will also need to add `#include
<asio/ssl/impl/src.hpp>`.

[heading Building the tests and examples on Linux or UNIX]

If the boost directory (e.g. the directory called `boost_1_34_1`) is in the
same directory as the asio source kit, then you may configure asio by simply
going:

  ./configure

in the root directory of the asio source kit. Note that configure will always
use the most recent boost version it knows about (i.e. 1.34.1) in preference to
earlier versions, if there is more than one version present.

If the boost directory is in some other location, then you need to
specify this directory when running configure:

  ./configure --with-boost=``['path_to_boost]``

When specifying the boost directory in this way you should ensure that you use
an absolute path.

To build the examples, simply run `make` in the root directory of the asio
source kit. To also build and run the unit tests, to confirm that asio is
working correctly, run `make check`.

[heading Building the tests and examples with MSVC]

To build using the MSVC 9.0 (or later) command line compiler, perform the
following steps in a Command Prompt window:

* If you are using a version of boost other than 1.34.1, or if the boost
  directory (i.e. the directory called `boost_1_34_1`) is not in the same
  directory as the asio source kit, then specify the location of boost by
  running a command similar to [^set BOOSTDIR=['path_to_boost]]. Ensure that
  you specify an absolute path.

* Change to the asio `src` directory.

* Execute the command `nmake -f Makefile.msc`.

* Execute the command `nmake -f Makefile.msc check` to run a suite of tests to
  confirm that asio is working correctly.

[heading Building the tests and examples with MinGW]

To build using the MinGW g++ compiler from the command line, perform the
following steps in a Command Prompt window:

* If you are using a version of boost other than 1.34.1, or if the boost
  directory (i.e. the directory called `boost_1_34_1`) is not in the same
  directory as the asio source kit, then specify the location of boost by
  running a command similar to [^set BOOSTDIR=['path_to_boost]]. Ensure that
  you specify an absolute path using ['forward slashes] (i.e.
  `c:/projects/boost_1_34_1` rather than `c:\projects\boost_1_34_1`).

* Change to the asio `src` directory.

* Execute the command `make -f Makefile.mgw`.

* Execute the command `make -f Makefile.mgw check` to run a suite of tests to
  confirm that asio is working correctly.

[note The above instructions do not work when building inside MSYS. If you want
to build using MSYS, you should use [^export] rather than [^set] to specify the
location of boost.]

[heading Macros]

The macros listed in the table below may be used to control the behaviour of
Asio.

[table
  [[Macro][Description]]
  [
    [`ASIO_ENABLE_BUFFER_DEBUGGING`]
    [
      Enables Asio's buffer debugging support, which can help identify when
      invalid buffers are used in read or write operations (e.g. if a
      std::string object being written is destroyed before the write operation
      completes).

      When using Microsoft Visual C++ 11.0 or later, this macro is defined
      automatically if the compiler's iterator debugging support is enabled,
      unless `ASIO_DISABLE_BUFFER_DEBUGGING` has been defined.

      When using g++, this macro is defined automatically if standard library
      debugging is enabled (`_GLIBCXX_DEBUG` is defined), unless
      `ASIO_DISABLE_BUFFER_DEBUGGING` has been defined.
    ]
  ]
  [
    [`ASIO_DISABLE_BUFFER_DEBUGGING`]
    [
      Explictly disables Asio's buffer debugging support.
    ]
  ]
  [
    [`ASIO_DISABLE_DEV_POLL`]
    [
      Explicitly disables [^/dev/poll] support on Solaris, forcing the use of
      a `select`-based implementation.
    ]
  ]
  [
    [`ASIO_DISABLE_EPOLL`]
    [
      Explicitly disables `epoll` support on Linux, forcing the use of a
      `select`-based implementation.
    ]
  ]
  [
    [`ASIO_DISABLE_EVENTFD`]
    [
      Explicitly disables `eventfd` support on Linux, forcing the use of a
      pipe to interrupt blocked epoll/select system calls.
    ]
  ]
  [
    [`ASIO_DISABLE_KQUEUE`]
    [
      Explicitly disables `kqueue` support on macOS and BSD variants,
      forcing the use of a `select`-based implementation.
    ]
  ]
  [
    [`ASIO_DISABLE_IOCP`]
    [
      Explicitly disables I/O completion ports support on Windows, forcing the
      use of a `select`-based implementation.
    ]
  ]
  [
    [`ASIO_DISABLE_THREADS`]
    [
      Explicitly disables Asio's threading support, independent of whether or
      not Boost supports threads.
    ]
  ]
  [
    [`ASIO_NO_WIN32_LEAN_AND_MEAN`]
    [
      By default, Asio will automatically define `WIN32_LEAN_AND_MEAN` when
      compiling for Windows, to minimise the number of Windows SDK header files
      and features that are included. The presence of
      `ASIO_NO_WIN32_LEAN_AND_MEAN` prevents `WIN32_LEAN_AND_MEAN` from
      being defined.
    ]
  ]
  [
    [`ASIO_NO_NOMINMAX`]
    [
      By default, Asio will automatically define `NOMINMAX` when compiling for
      Windows, to suppress the definition of the `min()` and `max()` macros.
      The presence of `ASIO_NO_NOMINMAX` prevents `NOMINMAX` from being
      defined.
    ]
  ]
  [
    [`ASIO_NO_DEFAULT_LINKED_LIBS`]
    [
      When compiling for Windows using Microsoft Visual C++ or Borland C++, Asio
      will automatically link in the necessary Windows SDK libraries for sockets
      support (i.e. [^ws2_32.lib] and [^mswsock.lib], or [^ws2.lib] when
      building for Windows CE). The `ASIO_NO_DEFAULT_LINKED_LIBS` macro
      prevents these libraries from being linked.
    ]
  ]
  [
    [`ASIO_ENABLE_CANCELIO`]
    [
      Enables use of the `CancelIo` function on older versions of Windows. If
      not enabled, calls to `cancel()` on a socket object will always fail with
      `asio::error::operation_not_supported` when run on Windows XP, Windows
      Server 2003, and earlier versions of Windows. When running on Windows
      Vista, Windows Server 2008, and later, the `CancelIoEx` function is
      always used.

      The `CancelIo` function has two issues that should be considered before
      enabling its use:

      * It will only cancel asynchronous operations that were initiated in the
        current thread.

      * It can appear to complete without error, but the request
        to cancel the unfinished operations may be silently ignored by the
        operating system. Whether it works or not seems to depend on the
        drivers that are installed.

      For portable cancellation, consider using one of the following
      alternatives:

      * Disable asio's I/O completion port backend by defining
        ASIO_DISABLE_IOCP.

      * Use the socket object's close() function to simultaneously
        cancel the outstanding operations and close the socket.
    ]
  ]
  [
    [`ASIO_NO_TYPEID`]
    [
      Disables uses of the `typeid` operator in asio. Defined automatically if
      `BOOST_NO_TYPEID` is defined.
    ]
  ]
  [
    [`ASIO_HASH_MAP_BUCKETS`]
    [
      Determines the number of buckets in asio's internal `hash_map` objects.
      The value should be a comma separated list of prime numbers, in ascending
      order. The `hash_map` implementation will automatically increase the
      number of buckets as the number of elements in the map increases.

      Some examples:

      * Defining `ASIO_HASH_MAP_BUCKETS` to `1021` means that the `hash_map`
        objects will always contain 1021 buckets, irrespective of the number of
        elements in the map.

      * Defining `ASIO_HASH_MAP_BUCKETS` to `53,389,1543` means that the
        `hash_map` objects will initially contain 53 buckets. The number of
        buckets will be increased to 389 and then 1543 as elements are added to
        the map.
    ]
  ]
]

[heading Mailing List]

A mailing list specifically for Asio may be found on
[@http://sourceforge.net/mail/?group_id=122478 SourceForge.net]. Newsgroup
access is provided via [@http://dir.gmane.org/gmane.comp.lib.boost.asio.user
Gmane].

[heading Wiki]

Users are encouraged to share examples, tips and FAQs on the Asio wiki,
which is located at [@http://think-async.com/Asio/].

[endsect]
