|  | 
This section lists platform-specific implementation details, such as the default demultiplexing mechanism, the number of threads created internally, and when threads are created.
Demultiplexing mechanism:
select for demultiplexing.
            This means that the number of file descriptors in the process cannot
            be permitted to exceed FD_SETSIZE.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
epoll for demultiplexing.
          Threads:
epoll
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
/dev/poll for demultiplexing.
          Threads:
/dev/poll is performed in one
            of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
select for demultiplexing.
            This means that the number of file descriptors in the process cannot
            be permitted to exceed FD_SETSIZE.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
kqueue for demultiplexing.
          Threads:
kqueue
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
kqueue for demultiplexing.
          Threads:
kqueue
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
select for demultiplexing.
            This means that the number of file descriptors in the process cannot
            be permitted to exceed FD_SETSIZE.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
select for demultiplexing.
            This means that the number of file descriptors in the process cannot
            be permitted to exceed FD_SETSIZE.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
select for demultiplexing.
            This means that the number of file descriptors in the process cannot
            be permitted to exceed FD_SETSIZE.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
min(64,IOV_MAX) buffers may be transferred in a single
            operation.
          Demultiplexing mechanism:
select for demultiplexing.
          Threads:
select
            is performed in one of the threads that calls io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
Demultiplexing mechanism:
select for emulating
            asynchronous connect.
          Threads:
io_service::run(), io_service::run_one(), io_service::poll() or io_service::poll_one().
          io_service
            is used to trigger timers. This thread is created on construction of
            the first deadline_timer
            or deadline_timer_service
            objects.
          io_service
            is used for the select
            demultiplexing. This thread is created on the first call to async_connect().
          io_service
            is used to emulate asynchronous host resolution. This thread is created
            on the first call to either ip::tcp::resolver::async_resolve() or ip::udp::resolver::async_resolve().
          Scatter-Gather:
Asio provides limited support for the Windows Runtime. It requires that the language extensions be enabled. Due to the restricted facilities exposed by the Windows Runtime API, the support comes with the following caveats:
io_service,
            strand, buffers, composed
            operations, timers, etc., should all work as normal.
          cancel()
            function is not supported for sockets. Asynchronous operations may only
            be cancelled by closing the socket.
          null_buffers
            are not supported.
          tcp::no_delay and socket_base::keep_alive
            options are supported.
          Demultiplexing mechanism:
Windows::Networking::Sockets::StreamSocket class to implement asynchronous
            TCP socket operations.
          Threads:
io_service for
            the handler to be executed.
          io_service
            is used to trigger timers. This thread is created on construction of
            the first timer objects.
          Scatter-Gather: