Before you start

Purpose of this documentation

This guide assists you in rapidly developing your VoIP application with Zoiper SDK 2.0. This manual contains an overview of the entities in the SDK with a lot of practical examples of implementation, usage and configuration.

Jump to the section of your interest:


To enjoy the powerful benefits of Zoiper SDK 2.0, you need a license. Depending on your needs, you can buy 2 different types of licenses:

  • Installation license per end-user
  • Unlimited installations;

Please contact Zoiper for more details and test licenses or to receive licenses for testing purposes.

Threading model

Zoiper SDK 2.0 is thread-safe. Shared objects can be called simultaneously from multiple threads. All callbacks from the SDK modules to the application code are performed in the context of the application thread which invokes the respective functions and methods.

In order to receive callbacks, the SDK needs to receive processing time from your application core. You can achieve this by invoking the respective functions.

On Android, iOS, and macOS, the main UI thread usually handles the assignment of processing time to the SDK.

Regarding sockets and transports, the SDK manages and utilizes the threads internally. For the interaction with sockets and transports, the SDK also internally manages and utilizes its own separate thread. As a result, the application code can use the processing time without blocking the SDK sockets.

More resources

Inside the SDK packages, you can find the respective reference and examples of basic usage for all:

  • methods
  • functions
  • APIs
  • callbacks
  • etc.

Third-party software

The SDK is (partially) built with:

  • JThread, Copyright © 2000-2005 Jori Liesenborgs
  • JRTPLIB, part of JRTPLIB Copyright © 1999-2005 Jori Liesenborgs
  • GSM, Copyright 1992, 1993, 1994 by Jutta Degener and Carsten Bormann, Technische Universitaet Berlin
  • SPEEX The Xiph OSC and the Speex Parrot logos are trademarks (TM) of Xiph.Org
  • OpenLDAP, Copyright 1999-2003 The OpenLDAP Foundation, Redwood City, California, USA. All Rights Reserved
  • PortAudio, Copyright © 1999-2002 Ross Bencina and Phil Burk
  • PortMixer, PortMixer, Windows WMME Implementation, Copyright © 2002, Written by Dominic Mazzoni and Augustus Saunders
  • Resiprocate, The Vovida license The Vovida Software License, Version 1.0, Copyright © 2000 Vovida Networks, Inc. All rights reserved
  • OpenSSL, Copyright © 1998-2019 The OpenSSL Project. All rights reserved. Copyright © 1995-1998 Eric Young All rights reserved
  • c-ares, Copyright © 1998 by the Massachusetts Institute of Technology. Copyright © 2007 - 2018, Daniel Stenberg with many contributors, see AUTHORS file
  • curl, Copyright © 1996 - 2022, Daniel Stenberg,, and many contributors, see the THANKS file. All rights reserved
  • Jansson, Copyright © 2009-2020 Petri Lehtinen
  • JsonCpp, Copyright © 2007-2010 Baptiste Lepilleur and The JsonCpp Authors
  • LAME, Copyright © 1991 Free Software Foundation, Inc.
  • Libevent, Copyright © 2000-2007 Niels Provos Copyright © 2007-2012 Niels Provos and Nick Mathewson
  • libvpx, Copyright © 2010, The WebM Project authors. All rights reserved
  • Magic Enum C++, Copyright © 2019 - 2021 Daniil Goncharov
  • Оpus, Copyright © 2001-2011 Xiph.Org, Skype Limited, Octasic, Jean-Marc Valin, Timothy B. Terriberry, CSIRO, Gregory Maxwell, Mark Borgerding, Erik de Castro Lopo
  • Protocol Buffers (a.k.a., protobuf), Copyright © 2008 Google Inc. All rights reserved
  • RNNoise, Copyright © 2017, Mozilla. Copyright © 2007-2017, Jean-Marc Valin. Copyright © 2005-2017, Xiph.Org Foundation. Copyright © 2003-2004, Mark Borgerding
  • libSRTP, Copyright © 2001-2017 Cisco Systems, Inc. All rights reserved
  • WebRTC, Copyright © 2011, The WebRTC project authors. All rights reserved
  • ICU, Copyright © 1991-2022 Unicode, Inc. All rights reserved

Please contact for more information.