Hi Vinnie, I have followed your stuff since you were on the Juce Forum (audio plugin developer here) and I was wondering if you ever took a look at https://github.com/mefyl/elle It's a network library that use coroutine and boost asio I was quite impressed when I saw a demo of it at a French c++ user Group. just my 2 cents. Le 14/03/2019 à 17:48, Vinnie Falco via Boost-users a écrit :
Fellow C++, Boost, and WG21 Enthusiasts, lend me your ear!
I write to inform you about exciting developments in C++ networking.
First, a bit of background. Networking comes in three flavors:
* Networking TS https://cplusplus.github.io/networking-ts/draft.pdf * Boost.Asio https://www.boost.org/doc/libs/1_69_0/doc/html/boost_asio.html * Standalone Asio https://github.com/chriskohlhoff/asio
These three are for the most part identical, except that Asio flavors have additional features like ssl::stream and signal_set which are not in the TS, but will very likely appear in a future update or version. We've had Asio for over a decade now, but there is a shortage of experts. Some people believe this shortage is because Asio in particular (and thus, Networking TS since they have identical interfaces) is "difficult to use." I believe it is wrong to blame Asio for this. Concurrent programs in general are hard to write. This is applicable:
"Unfortunately, today's reality is that only thoughtful experts can write explicitly concurrent programs that are correct and efficient. This is because today's programming models for concurrency are subtle, intricate, and fraught with pitfalls that easily (and frequently) result in unforeseen races (i.e., program corruption) deadlocks (i.e., program lockup) and performance cliffs (e.g., priority inversion, convoying, and sometimes complete loss of parallelism and/or even worse performance than a single-threaded program). And even when a correct and efficient concurrent program is written, it takes great care to maintain — it's usually brittle and difficult to maintain correctly because current programming models set a very high bar of expertise required to reason reliably about the operation of concurrent programs, so that apparently innocuous changes to a working concurrent program can (and commonly do, in practice) render it entirely or intermittently nonworking in unintended and unexpected ways. Because getting it right and keeping it right is so difficult, at many major software companies there is a veritable priesthood of gurus who write and maintain the core concurrent code." - Herb Sutter, "The Trouble with Locks", http://www.drdobbs.com/cpp/the-trouble-with-locks/184401930
Although this was written in 2005 it is still relevant today. It is understandable that Asio will be the first target of anger and frustration when writing concurrent programs, since it is on the "front line" so to speak. There has also been a distinct shortage of *good* tutorials and examples for Asio. Articles or blog posts which teach you step by step, explaining everything, and giving example code which demonstrates best practices.
Boost.Beast is my low-level HTTP/WebSocket library which builds on Boost.Asio: https://github.com/boostorg/beast
In the original release of Beast, the documentation stated "prior understanding of Boost.Asio is required." However, field experience has shown that users ignore that requirement and attempt to write complex, concurrent programs as their first-time introduction to both Beast and Asio. Based on feedback from committee members, and to serve users better, the scope of Beast has been enlarged to include first-time users of networking. The upcoming Boost 1.70 release reflects this new scope and I am excited to announce some very nice things which you can access today.
First of all, Beast documentation and examples no longer use the "boost::asio" namespace, they the namespace alias "net::". While this is cosmetic, it reinforces the notion when inspecting code that it is equally applicable to Boost.Asio, Asio, and Networking TS (identifiers which are not in the TS, such as signal_set, are still qualified with boost::asio).
A new documentation page explains the three flavors of networking:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io.htm...
This is also explained in my 2018 CppCon presentation:
https://youtu.be/7FQwAjELMek?t=444
I have added a "Networking Refresher", a complete overview of networking from soup to nuts. No prior knowledge or understanding of networking is required, everything is explained in detail so if you want to learn this is the place to start. I also kept it short, but it is loaded with hyperlinks for further learning:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/asi...
There was a recent paper in Kona, P1269R0 ("Three Years with the Networking TS") about difficulty of implementing timeouts. To address this, Beast now has a stream class which implements configurable timeouts for you, and callers no longer have to fiddle with timers manually anymore. Everything "Just Works." It achieves the P1269R0 author's goal of having timeouts "built-in to asynchronous operations", but in a way that fits in with the design of the TS:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/tim...
I feel that this `beast::basic_stream` serves as an existence proof that the current design of Networking TS is sound - the TS offers a flexible toolbox which lets you build your own framework the way that you want it, without making odd choices for you. We are still discovering ways of leveraging it to maximum use. The beast::websocket::stream also has built-in timeouts, but they are enhanced to support "idle pings" (keeping client connections alive) and everything is fully configurable:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_websoc...
All you need to do to get sensible, suggested websocket timeouts is add one line of code after creating your stream:
ws.set_option(websocket::stream_base::timeout::suggested( beast::role_type::server));
To address the cumbersome boilerplate of writing composed operations (specifically the need to propagate the associated allocator and associated executor, and to avoid invoking the completion handler from within the initiating function when the operation would complete immediately) Beast adds two new utility base classes, with plentiful documentation and examples throughout:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wri...
There are two well-rounded examples which show you step by step how to write these things in a safe way:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wri...
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/wri...
I have a big, new open source project which implements a server, that uses the `system_context`, taking full advantage of native Windows and Mac OS system-level execution context features. To support this use case and industry feedback, the examples in Beast now default to being always thread-safe. All examples use a "strand", and leverage P1322R0 ("Networking TS enhancement to enable custom I/O executors"). Yes, this paper which was approved in Kona, is now implemented in both Boost.Beast, and Boost.Asio, including all of the Beast examples, so if you pick up Boost 1.70 (or the master branches from github) you can start playing with this as soon as you're done reading this message!!
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1322r0.html
We have an active #beast channel in the C++ Slack (https://slack.cpp.al) where experienced users can help, no question is too small! I hope you will join me and the rest of the Beast and Asio community in exploring what the very powerful Networking TS and Asio libraries have to offer, and build something great together!
Regards
P.S. Don't forget to star the repository! https://github.com/boostorg/beast _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org https://lists.boost.org/mailman/listinfo.cgi/boost-users
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