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, 12 Mar 2005 CPOL
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VOIP using Microsoft TAPI


I use Microsoft TAPI 3.0 to make video and voice communicating applications. This project was edited using Visual Studio .NET. Microsoft Platform SDK is needed to compile.

VOIP simple test map:

  • Direct PC to PC case: two PCs, VideoIPPHONE
  • PC to PC through Gatekeeper(H.323) case: Gatekeeper(H.323), two PC, VideoIPPHONE
  • PC to PSTN case: Gateway(H.323), Gatekeeper(H.323), one PC, VideoIPPHONE, telephone


You can get the Microsoft TAPI 3.0 information from here.

You can make VOIP that uses SIP or H.323 Protocol.

SIP protocol opensource site is Vovida.

H.323 protocol opensource site is openh323.

Using the Code

Try connection to acceptor.

CMsTapiOutgoing    outgoing.StartMsTapi(4, wszIpAddress); 
// 4 is option for LAN .

Answer from sender:

CMsTapiIncoming    incoming.AnswerTheCall();

Session halt:

CMsTapiIncoming    incoming.EndMsTapi();
CMsTapiOutgoing    outgoing.EndMsTapi();

Points of Interest

Microsoft TAPI 3.0 has a bug.
When the application communicates to PSTN terminal through the CISCO H.323 gateway, the application or PSTN terminal sends sound one way only.
It is because during communication through RTP port is divided.

CISCO H.323 Gateway

  • RTP: 5000
  • RTCP: 5001

Microsoft TAPI

  • RTP: 5002
  • RTCP: 5001


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Park NoYoon
Software Developer interpay
Korea (Republic Of) Korea (Republic Of)
No Biography provided

Comments and Discussions

GeneralMy vote of 3 PinmemberMic6-Aug-13 15:27 
Generalvoip sip Pinmemberdan rogy19-Sep-10 10:42 
GeneralHi Pinmembergsandeep1006-Nov-09 3:26 
GeneralHelp Pinmembermicro2412-Apr-09 21:27 
QuestionI have a question about your program.^^ Pinmemberjunsungahn16-Jan-09 2:13 
GeneralHelp. PinmemberPratiksha Saxena2-Nov-08 20:49 
GeneralRe: Help. PinmemberPark NoYoon3-Nov-08 19:22 
GeneralRe: Help. PinmemberPratiksha Saxena3-Nov-08 19:51 
i have windows XP.
I tried running exe but its not working.
Please help...

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