Re: inter-process communication

From:

"David Ching" <dc@remove-this.dcsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 8 Oct 2007 08:11:24 -0700

Message-ID:

<9LrOi.2249$sm6.578@nlpi069.nbdc.sbc.com>

"AliR (VC++ MVP)" <AliR@online.nospam> wrote in message
news:vnrOi.4687$oA2.3381@nlpi068.nbdc.sbc.com...

I would go with the callback. It is more reliable, and easier. SendMessage
with HWND_BROADCAST will only be sent to the top level window of each
application, and if the code that handles that event is not in the main
window, then you will have to do alot of redirecting.

Callback function will get all the information to whoever is asking for
it.

2 problems with callback: 1) it is called in the context of the calling
process, which may or may not be OK (e.g. if callee wants to update UI
windows in response to the callback, it cannot do so directly since it's not
running on the callee's primary thread); 2) If pointers are required to pass
info to the callees, they are not automatically marshalled.

I use PostMessage(WM_COPYDATA, ....) and pass a GlobalAlloc()'d struct
containing info to the callee; the callee is responsible for freeing the
memory using GlobalFree() or whatever other memory management scheme is used
that allows one process to create it and another to free it.

-- David