by Greg Fox (1 Submission)
Category: Windows API Call/Explanation
Difficulty: Advanced
Date Added: Wed 3rd February 2021
Rating: 
(2 Votes)
Obtain Caller ID information via the TAPI API
Assumes
TAPI Caller ID Project
---------------------------------
Gregory Fox
8/28/2007
[email protected]
VB6 Project Group: _LevelA_TAPITest_GRP.vbg
Structure: ActiveX DLL with test form EXE
Uses: TAPI 2.0.2
The TAPI CallerID OCX I was using does not work with Win2003 Server,
so I decided to bite the bullet and see if I could dive into the
TAPI API from VB6.
It would have been easier to just buy another OCX, I suppose, but...
This project falls into the category of "you would think some simple examples
would be easily found on Google - but are not." I did find several starting
points which helped, namely code samples from (1) Ray Mercer and
(2) Brian Yule (on www.planet-source-code.com). Thanks for their posts.
I am posting this code as-is, so other Googlers can find help more easily.
This is a simple proof-of-concept program for getting Caller ID info from
a TAPI-compliant device. As I am not a TAPI API expert, there are many
aspects to this of which I am not aware (and not sure I need to be).
For example:
(1) I noticed (comments in the code) that the time delay between hanging
up and the LINECALLSTATE_IDLE msg is very long (about 5 sec). If a new
call comes in during this period, TAPI uses the SAME call structure.
Not sure if there is a simple way around it (like setting the idle delay),
so I coded around it, looking for changes to the CID info.
(2) With my laptop's modem, I get two LINE_CALLINFO msgs which appear to
be identical. Not sure if this is common, but even if not it needs to be
addressed (the fix for (1) also fixes this).
I am not providing a step-by step document. Coders should easily be able to
follow my code and the architecture to learn from it. The basic thing I
needed to learn first was the order of initialization/shut-down, and the
content of the callback method parms.
To use the test window:
1. Select proper device from the combo box
2. Click on <Listen>
3. Call your TAPI modem's line: note the debug window and the CID text box
4. Click on <Close> to disconnect
There were several important changes I needed to make to sample code snippets
that I found. First, padding in several of the UDT's needed to be in the
form of byte arrays - not fixed-len strings. Don't ask me why. Crashed
otherwise. Second, several code samples stored the obj ptr to the main class
in a global numerical variable. Can't do that! More crashes.
Coder Notes:
This structure has a DLL with 2 public classes:
CTAPIDeviceList - for enumeration of the device desc (also public)
CTAPICID - for caller ID info events
The main class in the DLL (as a singleton) is CTAPIAPP,
which is instantiated in Sub Main()
This is the structure I prefer for such components. Additional
functionality would require more public classes to encapsulate CTAPICID
Download TAPI Caller ID (30 KB)
VBcoders