boost.asio - asynchronous io

7/23/2019 Boost.asio - Asynchronous IO

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Asynchronous I/O withBoost.Asio

What are asynchronous operations?

When shall I use Boost.Asio (and not threads)?

How do I use Boost.Asio?

How does Boost.Asiosarchitecture look like?

What else do I need to know about Boost.Asio?

Boris Schling, [email protected]

Meeting C++, Dsseldorf, 10 November 2012


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Asynchronous operations

Asynchronous I/O with Boost.Asio 2

do_sync()

do_async (&done)

event_loop()

done()

A library like Boost.AsioYour code


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Boost.Asio vs. Boost.Thread


do_async (&done)

event_loop()

done()

A library like Boost.AsioYour code

Use asynchronous operations to access re-

sources concurrently outside of your process


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Boost.Asio vs. Boost.Thread


Your code

Use threads to access resources

concurrently in your process

block()


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Boost.Asio sample program


voidhandler(const boost::system::error_code &ec) {}

intmain()

{

boost::asio::io_service io_service;

boost::asio::deadline_timer timer(io_service,

boost::posix_time::seconds(5));

timer.async_wait(handler);

io_service.run();}


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Boost.Asio sample program





io_service.run();

async_wait() returns immediately

deadline_timer is one of many classes

in Boost.Asio which make it possible

to call functions asynchronously

run() calls handler after 5 seconds


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Asynchronous operations


deadline_timer

ip::tcp::acceptor

ip::tcp::resolver

ip::tcp::socket

async_wait() to wait until some time is expired

async_accept() to accept TCP/IP connections

async_resolve() to resolve hostnames

async_read_some() and async_write_some()to send and receive data

Boost.Asio provides different classes which turn

different blocking functions into asynchronous functions


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Boost.Asio terminology


voidhandler(const boost::system::error_code &ec) {}

intmain()

{





io_service.run();}

I/O service object

I/O object


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Boost.Asio terminology


deadline_timer io_service

An I/O object is initialized

with an I/O service object.

It doesnt use the I/O serviceobject thoughit uses

services provided by the I/O

service object.

An I/O service object

provides services to I/O

objects. Think of it as a set ofservicesset because there

is maximum one instance of

each and every service.

While I/O objects and I/O service objects are

visible in user code, I/O services do the hard work

in the background.


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Boost.Asio architecture


I/O service B

I/O service object

I/O service A

I/O object 3I/O object 2I/O object 1


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Boost.Asio architecture


boost::asio::

deadline_timer_service

boost::asio::

io_service

boost::asio::

stream_socket_service

boost::asio::

basic_deadline_timer

boost::asio::ip::tcp::

basic_socket_iostream

boost::asio::ip::tcp::

basic_stream_socket


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Multiple async operations


...


boost::asio::deadline_timer timer1(io_service,


boost::asio::deadline_timer timer2(io_service,


timer1.async_wait(handler);

timer2.async_wait(handler);

io_service.run();...


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Boost.Asio with threads


...





boost::thread t([&io_service]{ io_service.run(); });

io_service.run();

t.join();

...


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Synchronization with strand


...

boost::asio::io_service::strand strand(io_service);

timer1.async_wait(strand.wrap(handler));

timer2.async_wait(strand.wrap(handler));

boost::thread t([&io_service]{ io_service.run(); });

io_service.run();

t.join();

...


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No return with work


...


boost::asio::io_service::work work(io_service);

io_service.run();

...


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More information

50 Boost C++ Libraries in 180 minutes 16

Boost.Asio documentation:http://www.boost.org/libs/asio/

BoostCon presentations:http://boostcon.boost.org/presentations/

Thinking asynchronously (Chris Kohlhoff, 2011)

Creating Boost.Asio extensions (Boris Schling, 2011)

Online book:http://en.highscore.de/cpp/boost/asio.html

http://www.highscore.de/cpp/boost/asio.html(German)

http://zh.highscore.de/cpp/boost/asio.html (Chinese)

JTC1/SC22/WG21 paper N3388:http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3388.pdf
http://www.boost.org/libs/asio/http://boostcon.boost.org/presentations/http://en.highscore.de/cpp/boost/asio.htmlhttp://www.highscore.de/cpp/boost/asio.htmlhttp://zh.highscore.de/cpp/boost/asio.htmlhttp://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3388.pdfhttp://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3388.pdfhttp://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3388.pdfhttp://www.open-std.org/JTC1/SC22/WG21/docs/papers/2012/n3388.pdfhttp://zh.highscore.de/cpp/boost/asio.htmlhttp://www.highscore.de/cpp/boost/asio.htmlhttp://en.highscore.de/cpp/boost/asio.htmlhttp://boostcon.boost.org/presentations/http://boostcon.boost.org/presentations/http://www.boost.org/libs/asio/http://www.boost.org/libs/asio/

boost.asio - asynchronous io

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