Please post at least head of your header file...

Until then, this: googleing!

says this:

Insufficient info.
As usually, no function definitions in the header. Where are these functions bodies? The linker can't obtain them. Check out all sources, libraries and the project settings.

this is my header code, and I am including in the project:

[/********************************************************************/
/* */
/* C/C++ Header File (c) 2001 Avaya Global SME Solutions */
/* */
/* Contents:- */
/* IP Office Dev link DLL provides an interface for managing */
/* the IP Office product ranges from a Windows PC. */
/********************************************************************/
#ifndef _DEVLINK_H_
#define _DEVLINK_H_
typedef char TEXT;
#define DEVLINK_SUCCESS - 0
#define DEVLINK_UNSPECIFIEDFAIL 1
#define DEVLINK_LICENCENOTFOUND 2
#define DEVLINK_COMMS_OPERATIONAL 0
#define DEVLINK_COMMS_NORESPONSE 1
#define DEVLINK_COMMS_REJECTED 2
#define DEVLINK_COMMS_MISSEDPACKETS 3
#ifdef __cplusplus
extern "C"
{
#endif
typedef void (CALLBACK * CALLLOGEVENT)(
LONG pbxh,
TEXT * info
);
typedef void (CALLBACK * COMMSEVENT)(
LONG pbxh,
DWORD comms_state,
DWORD parm1
);
LONG PASCAL DLOpen( HANDLE pbxh
, TEXT * pbx_address
, TEXT * pbx_password
, TEXT * reserved1
, TEXT * reserved2
, COMMSEVENT cb
);
LONG PASCAL DLClose( LONG pbxh );
LONG PASCAL DLRegisterType2CallDeltas( LONG pbxh, CALLLOGEVENT cb );
#ifdef __cplusplus
};
#endif
#endif // _DEVLINK_H_]

I have the same name for these (DLOpen - DLClose) but even have the Link error...

Please, read my previous post again (and again ).
Where are these two functions DEFINED???
You post DECLARATIONS (prototypes) of these functions.

For example, I (header file) declare: I have 2000000000$.
You (linker) ask me: where are this lots of money?

this is my .cpp code where i call these functions, I'm including the
#include "devlink.h"
instruction and
#include "stdAfx.h"
that I read I need to get the Link

[#include "stdAfx.h"
#include <windows.h>
#include <stdio.h>
#include "devlink.h"
LONG hEvent;
DWORD dwCommsEvent;
BOOL bStarting;
void CALLBACK HandleCommsEvent( LONG pbxh, DWORD comms_evt, DWORD parm1 )
{
switch( comms_evt ) {
case DEVLINK_COMMS_OPERATIONAL:
// we are working fine... fall through
case DEVLINK_COMMS_NORESPONSE:
// system not found (initial connection),
// or network connection lost (rebooted?)
// fall through...
case DEVLINK_COMMS_REJECTED:
// incorrect system password specified...
if( bStarting ) {
dwCommsEvent = comms_evt;
SetEvent( hEvent );
}
else {
// insert your code here...
}
break;
case DEVLINK_COMMS_MISSEDPACKETS:
// Indicates that the system is under
// heavy load. IP Office always prioritises
// data routing and call handling above CTI events.
// (parm1 contains the number of packets missed)
break;
}
}
int main(int argc, char* argv)
{
printf( "connecting...");
bStarting = TRUE;
hEvent = CreateEvent( NULL, FALSE, FALSE, NULL );
DLOpen( 0,
"255.255.255.255",
"systempassword",
NULL,
NULL,
HandleCommsEvent );
dwCommsEvent = DEVLINK_COMMS_NORESPONSE;
WaitForSingleObject( hEvent, 10000L ); // 10 seconds
bStarting = FALSE;
if( dwCommsEvent == DEVLINK_COMMS_OPERATIONAL ) {
printf("Connected OK\n");
}
else {
printf("Error connecting to IP Office\n");
}
DLClose( 0 );
CloseHandle( hEvent );
return 0;
}]

Ooh... I know English is not my native language but...

I'm not interesting where you CALL these functions.
My question was: where were these two functions defined? A function definition code looks like
Where is
???
Probably these functions were placed in the library. Did you attach this library to your project? Where is this library?..

these are in my header file (devlink.h) and the code is:


I'm including my header file (devlink.h) as part of my project, and put the instruction to "LINK"
#include "devlink.h"
in my .cpp code, (I send the complete code in previous messages)

I see you don't understand a difference between a function declaration (prototype) and a functions definition (header+body). The DLOpen function prototype in your header file is not the DLOpen function. It's a declaration only. You declare (to compiler): "See, I have this function elsewhere. Let this functions calls in my code below correspond the prototype". A prototype does not generate machine code. If you call DLOpen in your program, you must have this function definition (header+body) in your source codes or in an external library (included in the project).

Obviously you don't know where is DLOpen and where is DLClose source or object codes.
I don't know as well...

I found these functions in dlfcn.h and I need to add the cdefs,h
I include in my projects, but now I have this error:

Deleting intermediate files and output files for project 'prueba_IP_devlink_08 - Win32 Debug'.
--------------------Configuration: prueba_IP_devlink_08 - Win32 Debug--------------------
Compiling...
prueba_08.cpp
Linking...
dlfcn.h : fatal error LNK1136: invalid or corrupt file
Error executing link.exe.

prueba_IP_devlink_08.exe - 1 error(s), 0 warning(s)