[/
 / 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 Boost.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
Boost.Asio:

* Boost.System for the `boost::system::error_code` and
`boost::system::system_error` classes.

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

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

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

Furthermore, some of the examples also require the Boost.Thread,
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 Building Boost Libraries]

You may build the subset of Boost libraries required to use Boost.Asio and its
examples by running the following command from the root of the Boost download
package:

[pre
  b2 --with-system --with-thread --with-date_time --with-regex --with-serialization stage
]

This assumes that you have already built `b2`. Consult the Boost.Build
documentation for more details.

[/

[heading Compiling Programs With Boost.Asio]

Consider the following minimal Boost.Asio program [^simple.cpp]:

  #include <boost/asio.hpp>
  #include <iostream>
  #include <ostream>

  int main()
  {
    boost::asio::ip::tcp::iostream s("www.boost.org", "http");

    s << "GET / HTTP/1.0\r\n";
    s << "Host: www.boost.org\r\n";
    s << "\r\n" << std::flush;

    std::cout << s.rdbuf();

    return 0;
  }

The following compiler commands may be used to build the program (note that the
name of the `boost_system` library may vary depending on the compiler version):

[table
  [
    [OS]
    [Compiler]
    [Command]
  ]
  [
    [FreeBSD]
    [g++]
    [[^g++ -I['boost_root] -pthread simple.cpp -L['boost_root]/stage/lib -lboost_system-gcc]]
  ]
  [
    [Linux]
    [g++]
    [[^g++ -I['boost_root] -pthread simple.cpp -L['boost_root]/stage/lib -lboost_system-gcc41]]
  ]
  [
    [macOS]
    [g++]
    [[^g++ -I['boost_root] simple.cpp -L['boost_root]/stage/lib -lboost_system]]
  ]
  [
    [Solaris]
    [g++]
    [[^g++ -I['boost_root] simple.cpp -L['boost_root]/stage/lib -lboost_system -lsocket -lnsl -lpthread]]
  ]
  [
    [Windows]
    [MSVC 9.0]
    [[^cl /EHsc /GR /MT /I['boost_root] /D_WIN32_WINNT=0x500 simple.cpp /link /libpath:['boost_root]/stage/lib]]
  ]
]

]

[heading Optional separate compilation]

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

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

[heading Macros]

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

[table
  [[Macro][Description]]
  [
    [`BOOST_ASIO_ENABLE_BUFFER_DEBUGGING`]
    [
      Enables Boost.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 `BOOST_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
      `BOOST_ASIO_DISABLE_BUFFER_DEBUGGING` has been defined.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_BUFFER_DEBUGGING`]
    [
      Explictly disables Boost.Asio's buffer debugging support.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_DEV_POLL`]
    [
      Explicitly disables [^/dev/poll] support on Solaris, forcing the use of
      a `select`-based implementation.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_EPOLL`]
    [
      Explicitly disables `epoll` support on Linux, forcing the use of a
      `select`-based implementation.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_EVENTFD`]
    [
      Explicitly disables `eventfd` support on Linux, forcing the use of a
      pipe to interrupt blocked epoll/select system calls.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_KQUEUE`]
    [
      Explicitly disables `kqueue` support on macOS and BSD variants,
      forcing the use of a `select`-based implementation.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_IOCP`]
    [
      Explicitly disables I/O completion ports support on Windows, forcing the
      use of a `select`-based implementation.
    ]
  ]
  [
    [`BOOST_ASIO_DISABLE_THREADS`]
    [
      Explicitly disables Boost.Asio's threading support, independent of whether
      or not Boost as a whole supports threads.
    ]
  ]
  [
    [`BOOST_ASIO_NO_WIN32_LEAN_AND_MEAN`]
    [
      By default, Boost.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
      `BOOST_ASIO_NO_WIN32_LEAN_AND_MEAN` prevents `WIN32_LEAN_AND_MEAN` from
      being defined.
    ]
  ]
  [
    [`BOOST_ASIO_NO_NOMINMAX`]
    [
      By default, Boost.Asio will automatically define `NOMINMAX` when
      compiling for Windows, to suppress the definition of the `min()` and
      `max()` macros. The presence of `BOOST_ASIO_NO_NOMINMAX` prevents
      `NOMINMAX` from being defined.
    ]
  ]
  [
    [`BOOST_ASIO_NO_DEFAULT_LINKED_LIBS`]
    [
      When compiling for Windows using Microsoft Visual C++ or Borland C++, Boost.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 `BOOST_ASIO_NO_DEFAULT_LINKED_LIBS` macro
      prevents these libraries from being linked.
    ]
  ]
  [
    [`BOOST_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
        BOOST_ASIO_DISABLE_IOCP.

      * Use the socket object's close() function to simultaneously
        cancel the outstanding operations and close the socket.
    ]
  ]
  [
    [`BOOST_ASIO_NO_TYPEID`]
    [
      Disables uses of the `typeid` operator in Boost.Asio. Defined
      automatically if `BOOST_NO_TYPEID` is defined.
    ]
  ]
  [
    [`BOOST_ASIO_HASH_MAP_BUCKETS`]
    [
      Determines the number of buckets in Boost.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 `BOOST_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 `BOOST_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 Boost.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 Boost.Asio wiki,
which is located at [@http://think-async.com/Asio/].

[endsect]