Re: Ncat/Nsock on Windows; non-socket select()s

[doug () hcsw org]

On Tue, Aug 05, 2008 at 01:40:27PM -0500 or thereabouts, Kris Katterjohn wrote:
> The main problem getting Ncat to work is that Windows' select() doesn't work
> for non-socket descriptors (i.e. stdin).  This presents a problem in Ncat
> itself and Nsock.

Yes, this is a problem when writing win32 code: You can't use file descriptors
in place of sockets or vice-versa. This affects things like select() and
fdopen().

Although I've never done this before, one way to do it might be to open
a socket, then spawn a thread that basically does this:

while(1) {
  data = read_data_from_stdin();
  if (is_stdin_eof()) {
    close_the_socket();
    join_this_thread();
  }
  write_data_to_the_socket(data);
}

and then use select on the socket as usual in your main thread. This isn't as
crazy as it might sound because windows programmers use threads for everything.
(I think we could also use this hack to get select()able pcap descriptors on win32)

Alternatively, win32 does have some async APIs like WaitForMultipleObjects()
which you mentioned. There's also IO Completion Ports:

http://msdn.microsoft.com/en-us/library/ms810436.aspx

"WaitForMultipleObjects may indeed provide an alternative to I/O completion
 ports. However, I/O completion ports are much more flexible and easier to
 use than WaitForMultipleObjects."

"An IOCP is an object that can be associated with a number of I/O objects,
 such as files, named pipes, or sockets. When a thread requests input via
 the IOCP, the I/O system blocks the calling thread until any pending
 asynchronous I/O on any of the objects has completed."

Doug

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