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Robert Bamberg, Independent Software Developer

Windows Telephony Programming FAQ Page

Program: \telprog\chapter05\tMonitor

Problems building tMonitor Application
Problems running tMonitor Application

Problems building tMonitor Application
error C2664: 'GetIDFromPhone'
fatal error LNK1104: cannot open file...
error LNK2001: unresolved external symbol

Error C2664: 'GetIDFromPhone' : cannot convert parameter 2 from 'const struct HLINE__ *' to 'const struct HPHONE__ *'

People who had downloaded the source code that accompanies Chris's book Windows Telephony Programming from this website prior to May 28, 2002 had experienced problems trying to re-build the tMonitor application discussed in chapter 5 of Chris's book.

The error reported was as follows:

\telprog\Chapter05\tMonitor\IncomingCallDlg.cpp(165) : error C2664: 'GetIDFromPhone' : cannot convert parameter 2 from 'const struct HLINE__ *' to 'const struct HPHONE__ *'

To correctly fix this error you should change the function call ctDevice.GetIDFromPhone() to ctDevice.GetIDFromLine() using the same arguments. The code will then correctly rebuild and run. This bug has been fixed in the new download, which was updated on May 28, 2002.

Additional Information

Originally I did not catch this bug due to the build environment I was working in. When I first took over the job of hosting Chris's source code, I upgraded my system so that I was compiling with the latest release of Microsoft's Core SDK (Build 5.1.3590.2, Last Updated Nov. 2001) which contains updates to TAPI. In order to correctly compile the source code with these latest updates, I included under Directories Tab of the Visual Studio->Tools->Options menu item, the include and library paths for the newly installed Microsoft SDK files before any other include or library paths. This environment change allowed me to re-compile all of the sources without error.

When I remove these two path statements from my Visual Studio Directories environment, I too was able to see this error. After examining this error more closely I realized that this is due to an incorrect function call in the source file IncommingCallDlg.cpp. Once again the compiler is correct in the error it reports. The call to ctDevice.GetIDFromPhone() needs a HPHONE for its second argument, but the code is trying to pass a HLINE value. (i.e. ctCall->GetLine() == CtLine *, and CtLine->GetHandle == HLINE).

The reason why I was able to rebuild the sources when including the updated TAPI release files was due to a #define statement in the new tapi.h header file of the Core SDK. In this header there is a definition that reads:

#define DECLARE_OPAQUE32(name) typedef DWORD name

This statement through typedef statements, defines all handles (HLINE, HPHONE, etc...) to be of the same type, i.e. DWORD, which is why I did not originally catch the error. In older versions of tapi.h this definition is defined as:

#define DECLARE_OPAQUE32(name) struct name##__ { int unused; }; \ typedef const struct name##__ FAR* name

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LINK : fatal error LNK1104: cannot open file...

The reason for these types of errors is that the tMonitor application needs to link with libraries built from the tfx workspace, (i.e. \telprog\tfx). Before you will be able to build the tMonitor application, you first need to rebuild the tfx libraries.

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Error LNK2001: unresolved external symbol "public: struct HPHONE__ const * __thiscall CtPhone::GetHandle(void)const"

If the tfx libraries are built in one build environment, i.e. with latest TAPI updates from the Microsoft Core SDK, and the tMonitor application is built in a different build environment, i.e. using an earlier release of TAPI include and library files, or vice-versa, you will see these types of errors. Both the TFX and tMonitor sources must be compiled and linked with the same TAPI environment files.

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Problems running tMonitor Application
Greeting is not played or heard garbled
Recording never stops on Hangup/DTMF digit

Greeting is not played or is heard garbled

Although the greeting file that instructs the caller to leave a voice message should always play properly for you, reports of this greeting not being played or sounding garbled have been seen by some users.

This type of error was fixed by updating the modem and/or soundcard drivers. This type of problem has been seen mainly on systems running Windows 2000 and Windows XP.

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Recording never stops on Hangup/DTMF digit

Problem Description:

It has been reported that under Windows 2000 which uses the Unimodem 5 TSP, that the tMonitor application does not working correctly when in Take a Message mode.

Normally when calling into the tMonitor application, the user can either click the button for "Take A Message", or alternatively allow the application to receive 4 ring events. In either case the phone line is answered, and playback of greeting/wave_test.wav begins. After voice playback has completed the application begins recording the callers message.

Under Windows 98, after recording a message, the caller can press any DTMF key or hangup to stop the recording process. A wave file is saved in the .\Messages directory relative to where the executable is run. This directory is created if it does not already exist.

Although you would think that the application should work the same way under Windows 2000, there is a problem. While in the process of recording, the DISCONNECT and MONITOR events are not being seen by the application until after the default duration of 120 seconds expires. These events are blocked for some reason until after recording has timed out. I believe that the problem is most likely due to differences in Unimodem 5 which comes packaged with Windows 2000, and Unimodem V which is found on Windows 98 machines. In my own testing with other examples I have written I have found that there are slight differences between Unimodem V and Unimodem 5. They are not the same program.

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