What is Boost.Asio, and why we should use it

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Writing portable networking code in С++ is a problem with long history, and there are many libraries were developed that tried to solve this problem. But I can say, that Boost.Asio is the best implementation among existing. On the base of Boost.Asio some number of libraries and applications (libpion, cpp-netlib) were already implemented, and development of some new things is in progress. Beside this, on the top of Boost.Asio I had developed a filtering subsystem for web-filtering product SKVT "Dozor-Jet" aka WebBoss.

Boost.Asio has following main features:

• ability to write cross-platform networking code, working on the most of existing platforms - Windows, Unix-like, Tru64, QNX, etc..
• supports both IPv4 and IPv6
• support for TCP & UDP
• support for asynchronous operations
• provide std::iostream compatible interfaces
• support for SSL connections
• support for delayed operations (timers)

For me, main advantage of Boost.Asio (besides cross-platform work) is, that on each platform, it uses most effective strategy (epoll on Linux 2.6, kqueue on FreeBSD/MacOSX, Overlapped IO on MS Windows). Library also allows to use different strategies — synchronous and asynchronous to work with sockets, and allows usage of streaming input/output, compatible with std::iostream. And these strategies could be mixed in one application, for example, accept connections in asynchronous mode, and after that, start thread, which will do input/output in sync mode (see test-otpc.cpp example).

For demonstration of Boost.Asio's features I wrote (some of parts were adopted from Boost.Asio examples) several examples, implementing different data handling strategies (more examples could be found on the home page of Boost.Asio). I had used these examples for selection of appropriate data handling strategies in my own applications. All these examples implements "stupid" web-server, that read request and return back single page, independent of address, that was specified in request. Currently following examples are available (all source files include file common.h):

• test-mcmt.cpp — implements data handling strategy Many Connections/Many Threads - it starts several threads, each of them accepts connections and performs input/output in asynchronous mode;
• test-otpc.cpp — implements strategy One Thread per Connection - one thread accepts connections in asynchronous mode, and then starts thread, in which input/output performed in synchronous mode (code, performing this is in files test-otpc-conn.cpp & test-otpc-conn.hpp;
• test-otpc-tp.cpp — almost same as test-otpc.cpp, but instead of dedicated thread for every connection uses a pool of threads, implemented by threadpool library.

To build examples (all source code is at github you need at least boost version 1.35, that contain Boost.Asio.

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