Best documentation for Boost:asio?

Some nice documentation on boost including a chapter on asio can be found in a (free) boost book at http://en.highscore.de/cpp/boost/index.html. The chapter on asio provides a general overview and then goes as far as how to develop your own custom asio extensions. Really fantastic effort by Boris Schäling!

First, I've been using Boost.Asio for quite a while already -- and I share your concern. To address your question:

• There really is very scarce documentation about Boost.Asio aside from the introduction and tutorial. I am not the author, but this is mostly because there are just too many things to document for something as low-level as an Asynchronous IO Library.
• The examples give more away than the tutorials do. If you don't mind spending a little time looking at the different examples, I would think they should suffice to get you started. If you want to run away with it, then the reference documentation should help you a lot.
• Ask around in the Boost Users and Boost Developers mailing list if you're really stuck or looking for specific guidance. I'm pretty sure a lot of people will be willing to address your concerns on the mailing lists.

There are efforts (not part of Boost.Asio) to expose a lot of the functionality and possible alternative use cases. This at best is scattered around the web in blogs and other forms of non-packaged documentation.

One thing that is unclear and which will really need close coordination with the author and developers of the Boost.Asio library would be as far as extending and customizing it for a specific platform or adding specific new functionality. This should be improved though but the good thing is it's looking like Asio will be a reference implementation for a standard library technical report (for an asynchronous IO library in the STL) in the future.

I wrote two small articles that could be used as introductions to boost.asio. They are available from my site