I have a situation where at termination of my program, I am closing my socket, and then deleting the socket object. Note, we are using non-asynchronous (blocking) accesses at this point, boost is version 1.36. In some cases, the socket has had some data written to it, but that data is never received by the connected client - because I destroy the socket before the data is sent. So, SO_LINGER is the socket option that is supposed to solve all my worries (it should wait on close for any unsent data to be sent), however I am using it and there is no effect. I presume because I'm doing something wrong.

SO_LINGER is just forwarded as-is to the native socket API, so if it doesn't work there's some problem with the socket. What I couldn't understand from your description is whether you used sync. or async. i/o, and from what thread (same as close() or some other). Could you please clarify these points?

I've been reading over the documentation for Boost.Asio and as far as I can tell the documentation makes no mention whatsoever about using Asio for anything other than sockets programming.  Suppose I wanted to implemented a simple file transfer client (I say client because the server will not be in C++) that reads files off of the disk and sends them to the server.  I'd like to do it asynchronously.  What would be the basic steps needed to do this with Boost.Asio, if it is indeed even possible?  I'd specifically like it to use I/O Completion Ports on Windows if possible, and whatever on Linux.  I'd like to be able to configure the number of worker threads on the backend, so that for example I can read from N files at once, or from N different locations in the same file.  I'd also like to have a single "controller" thread that receives all the events regarding when reads or writes complete, so that I don't have to use any kind of locking to synchronize things.

As a final "nice-to-have", I'd like to be able to plug my own types of "actions" into the model, things that aren't really I/O but that I still want to execute asynchronously that would sit in between a completed disk read and the initiation of writing that same data to the socket.  Think, for example, of encrypting the file before sending.  I don't want to block on the encryption, so it would be nice if I could do that asynchronously and still be notified of its completion through the same interface.  I know I can do all this directly in windows (which is the only system api i'm intimately familiar with) via IOCP, so I'm hoping something similar can be achieved with Boost.Asio.

Thanks