[boost] [asio] async_close ? async_shutdown ?

Hi! I find the asio docs a little terse about what it has to say about close / shutdown. Will close always block? Will shutdown block? What puzzles me is that the doc say that close will cancel outstanding async calls. I assume this means calls from where I did not have received a callback handler, yes? May I conclude from this, that when I invoke close from the last callback (I know there are no more pending callbacks) that close will do a graceful shutdown, i.e. deliver all buffered data to the receiver? Is there an example showing how to do a graceful shutdown? Is there an example that demonstrates shutdown? Why are there no asyn_ versions of these operations available? Thank you Roland aka speedsnail