Merry Christmas and Happy New Year!

Dear colleagues and partners,

With sincere thanks and much appreciation for your great work and commitment, we wish you and your families all the joys of this holiday season. May all your wishes and dreams come true and may you feel this happiness all year round.

New softphone in Google Play

We are happy and proud to invite you to try our updated sample sip softphone for Android. The main updates are better video  and secure connection support. The latest softphone version is available at Google Play.


We often receive the following questions about our ABTO Software’s VoIP SIP SDK for Windows:

  • is it implemented as native SIP DLL SDK or as ActiveX (COM) object.
  • how to integrate SDK into own application.

The answer is that VoIP SIP SDK for Windows is implemented as ActiveX simple object and compiled into native dll. It means that SDK can be used as ActiveX (COM) component which requires registration on client computer via regsvr32 tool. But it is not a single way. The SDK also exports methods and can be used as native SIP DLL SDK without registration. Standard SDK setup contains source code of both implementations.

So, it means that VoIP SIP SDK for Windows can be used in your app via ActiveX interface and via native DLL interface (exported functions as SIP DLL SDK).

SIP ZRTP client

ABTO Software’s VoIP SIP SDK is proud to present a new feature – ZRTP support for mobile platforms: iOS and Android.Using our SDK you are able to build custom sip zrtp client for iOS and Android.

Currently realization allows ZRTP secure peer-to-peer connection. Also it works in the situation when sip server does not influence the messages that it transfers. We are working on other cases of such connections.

To try this feature and purchase our SDK please proceed to the contact form or download the corresponding SDK for iOS and Android.

Early media use

You can use VoIP SIP SDK to make a custom intercom.
Obviously you can make a connection to communicate before you open the door.
However, one of the basic features of this solution is to be able to see the person near door before actually making a connection.
This feature is typically called early media.

How to implement it for Android:

when received incoming call in Android app invoke method:
phone.answerCall(183, true);

This method sends to remote side SIP request “183 Session progress+SDP”,
which allows start sending audio\video in both directions, but call still not answered.
Then you can answer or reject call.
If you have more questions please contact us.

STUN use

We are receiving many questions about STUN use.

STUN means Session Traversal Utilities for  NAT (Network Address Translator).

When using STUN is a good idea: If you do not receive video and audio because remote side can not send media. The reason could be that SIP sends local IP address. So you can try to enable STUN and input one of the following settings:


If you have more questions please contact us.

VoIP Video SDK

ABTO Software offers a variety of VoIP products that support video call using H.263 and H.264 video codecs:

  • VoIP Video SDK for Windows

It supports a single video connection. Softphone can have up to 8 lines per sample (standard version) or up to 64 lines per sample (multi-line version). You can put one connection on hold and establish video connection via another line. Read more

  • Video Conference VoIP SIP SDK for Windows

It supports video conference between multiple (3+) connections by means of the client. This unique feature can not be provided by regular sip server, which supports only audio conference. Read more

  • VoIP Video SDK for iPhone

Currently it supports a single video connection. Read more

  • VoIP Video SDK for Android

Only single video connection at the moment. Read more

  • RTP Video SDK
RTP SDK provides ability to send/receive media (sound and video) by RTP protocol. Read more
  • Custom video softphone solutions
On the basis of our SDKs we can develop custom softphone solutions like intercom, baby watcher, video chats etc. Contact us to request an estimate.
  • Video Webphone

We can develop a custom webphone on the basis of Flash/HTML5 library. You can find more details on the corresponding pages.

Documentation update

We updated page with our documentation on VoIP SIP SDK and added document about RTP SDK. Have a look here!

Happy Easter 2014!

Dear customers and visitors of our website,

Congratulations and Happy Easter Holidays!

ABTO Software’s VoIP SIP SDK team

SDK update (Mar 04, 2014)

New version of VoIP SIP SDK v4.7 (build 27.02.2014) for Windows includes the following main changes:

276. Added new method GetSIPHeaderValueArr, returns array of values of specified header name.
277. Added ability to mute local video. See new method MuteLocalVideo
278. Improved method RetrieveExternalAddress. Now it returns IP and port.
278. Added new property AECDelayMs
279. Fixed possible crash when received incoming call during SDK initalization

To try the latest VoIP SIP SDK for Windows please proceed to the Download form.





Development Environments:

  • Visual C++ / C++ / C# .NET
  • VB.NET / VB 6.0
  • Java
  • JavaScript / HTML / HTML5
  • Flash
  • Borland Delphi

Company details:

ABTO Software is the only owner and distributor of VoIP SIP SDK. The company also develops other products and offers software development services. Read more on