message passing between windows

As already suggested, you should read the documentation of PostMessage (I wouldn't use SendMessage for communicating with another application). You should also have a look at RegisterWindowMessage[^] function documentation.

Other people have suggested using PostMessage to get data from one app to another. A handy message to post is WM_COPYDATA as it can carry an arbitrary lump of data from one process to another. This means you can design your own protocol between two apps in a fairly broad way.

If you're writing your code to run on Vista or later versions of windows you might also have to wrestle with ChangeWindowMessageFilterEx(). Vista filters out WM_COPYDATA messages between apps in a lot of cases and you have to explicitly say "Oi, I want to receive that message, bozo!"

Other ways you might like to try include memory mapped files (effectively shared memory between processes - again, it's a bit harder on Vista and later), named pipes or sockets (very portable if slower than other options).

Oh, and then there's RPC (remote procedure calls), COM (component object model), CORBA (like COM but with I can never remember what the acronym means - common object request broker rings a bell) and things like Java RMI (bit useless if you're not using Java).

Personally I'd start with sockets as they're portable and can be used between just about any two applications on the planet. They're also relatively easy to program compared to RPC and the like AND there's plenty of good textbooks around and example code on the net.

Cheers,

Ash

http://www.doc88.com/p-91073435363.html[^]