There was this special application that I wanted to intercept all Windows messages for a specific remote processor. For that, I came to SetWindowsHookEx function but in order to install this hook on an external application you cannot do that simply by calling this function inside your code because it will fail with the following error
ERROR_HOOK_NEEDS_HMOD
1428 (0x594)
Cannot set nonlocal hook without a module handle.In order to fix that at first I thought I need to create a DLL which contains the hook function and then inject that into every application that I need to intercept its messages. What I later found out was that this is not required
To shed some light in there there are two subjects around this, first, there is this DLL injection topic which you can use this function to inject some DLL into other programs and the second one is my application which intercepts events from other applications. For the first one you need to inject the dll which contains the codes you want to inject into the application you want, obviously.
But for the second application that I mentioned you just need to write your codes inside some dll and then just load that codes inside your application and because you wrote down the SetWindowsHookEx function and the hook callback inside the DLL main function your code will successfully execute and actually you don’t need to inject it into any other application so it is pretty straightforward.
Because at first, it seems to be so complicated I decided to write this down so I wouldn’t forget it later.
That it, enjoy and if it was helpful please send some feedback.
P.S.: SetWinEventHook Is a completely different Hook. What exactly it does is it reports the events regarding the window manager. To be more specific it reports events related to window creation and destruction, window resizing and losing, or getting Focus around different windows. But it would never give any response regarding the window internal messages.
Mark Jansen: WindowsHookEx GitHub Project
Stmxcsr: Reinventing the wheel, DLL Injection via SetWindowsHookExA
