Re: posix style DGRAM sockets with cygwin.dll

["Robert A. Mackie" <robert_mackie@mail.com>]

Mumit,

    Thank you for looking.  I'm sorry this I asked for your time on what turned
out to be a code inspection issue rather than a cygwin issue.  Since the unix
system on which it ran correctly uses network order for memory, the code worked
there, inspite of my error.  I should have been more vigilent.

Rob.

PS:  I'm very impressed with the value of cygwin.  I should free up from my
most urgent deadlines in the next month or so.  I plan to volunteer some effort
to help support cygwin at that point.  What a convenient set of tools and
library.

Mumit Khan wrote:

> "Robert A. Mackie" <robert_mackie@mail.com> writes:
> >
> > I'm trying to get a very simple UDP example ported to cygwin as a
> > starting point for some real code I expect to develop.  Everything
> > compiles and links, but the sockets don't communicate.  When built for
> > unix the same code works fine.  (unless I've introduced some small bug
> > trying to get it to work under cygwin.)  I notice I'm not the first to
> > say something like this.  The last person was using the -no-cygwin
> > option and was told to call WSAStartup.  I read as much documentation as
> > I could find.  It looked to me like that was not necessary when using
> > the posix calls, rather than the winsock calls.  (Maybe I'm wrong ?)
>
> If you're using -mno-cygwin, you're using Windows sockets (and you need
> WSAStartup); if you're *not* using -mno-cygwin, you're using POSIX sockets
> and obviously don't need the windows hacks, er features.
>
> > If I do need to initialize winsock explicitly, could you help me with a
> > couple of details? The only place that I see WSAStartup and WSACleanup
> > defined is in <Windows32/Sockets.h>.  This file seems to be set up for
> > an MSC compiler, and includes a bunch of other similar headers.  When I
> > include any of them and the standard headers I'm used to, I get all
> > sorts of re-definition collisions between the headers.  When I include
> > them without the standard headers, things like strerror aren't defined.
>
> You include winsock.h, not the internal headers, but *only* if you're using
> Windows sockets. If you're using Cygwin runtime, use the POSIX specs and
> forget about the windows headers (Cygwin runtime will do the right thing).
>
> It's quite unclear from your message what runtime you're trying to use
> and so on. If you could elaborate, we could try to help.
>
> As far as your code is concerned, there is at least one blatant bug I
> see right away --
>
>   server_address.sin_port        = htonl(SERVER_UDP_PORT);
>                                    ^^^^^ (should be htons)
>
> likewise in the other case. Just remember that sin_addr is htonl and
> sin_port is htons and life would be a lot easier.
>
> Perhaps you ought to check over your code a bit more and try again.
>
> Regards,
> Mumit