Building the SureVoIP App, Gavin Henry

Building the SureVoIP App. Gavin Henry, SureVoIP, Trusted UK VoIP service provider. Founder and MD

SureVoIP provide hosted VoIP, SIP trunking, SIP DIDs, PBX support, internet access (broadband and Ethernet), and providing / provisioning the physical phones. There’s a common theme in Gavin’s presentation to what we heard from other similar companies on the importance of ownership of network and technology in delighting customers.

BTW check out Gavin’s SE Radio Podcast, they have high profile interviewees in software engineering.

At TADSummit EMEA 2019 Gavin presented “Building the SureVoIP Notify App“. He gave the presentation remotely, who would have thought back then everyone in 2020 would be presenting remotely! In building the notify app Gavin kicked off an open source project, Dart SIP, a dart-lang version of the SIP UA stack, ported from JsSIP. There are now 11 contributors to the project with 300 commits. It’s a great example of the power of open source.

This year Gavin runs through the SureVoIP app, which includes communication services: video, voice and messaging. It’s a great recipe and experience share in building and owning your communications client, rather than rebranding someone else. In the tech stack Gavin described, Flutter and Firebase are popular choices at TADHack. The client wake-up issues are a significant headache, and it’s great to learn how Gavin has solved them. Please get involved in Dart SIP, you heard it first at TADSummit EMEA 2019 🙂

Slideshare is having difficulties today, here’s a direct link to Gavin’s slides.

Agenda Description

Gavin Henry will take you through all the components that were needed to build the SureVoIP app. Using the power of Flutter, one source code base can be used to power mobile, web and desktop app versions. The journey covers key open source projects created, enhancements to existing open source projects, adoption of open source building blocks with standards based technologies like OAuth2, PKCE, AppAuth, PushKit, CallKit, OpenSIPS, RFC8599, Biometrics, RESTful APIs, WebSockets, SIP, Push Notifications, FreeSWITCH, WebRTC and many more.

Gavin Henry is the founder of SureVoIP, an Internet Telephony Service Provider and has written most of the software that sticks it all together. His interests include all aspects of software engineering, identity management (especially around OpenLDAP), all layers of the network stack, systems programming and the free software ecosystem. Gavin has an engineering degree in Electronics and Communications and outside of software has a real passion for the field of bushcraft. He can be reached at or

Listen to some of his podcasts which also discuss key technologies used with leading industry security experts –

Gavin Henry

2 thoughts on “Building the SureVoIP App, Gavin Henry”

  1. Thank you Gavin for an amazing resource on how to build a communications client. What was the most unexpected discovery you made in building your client?

    1. Thanks Alan!

      I’d say the amount you actually learn and how it improves the rest of your supporting infrastructure and software ecosystem. Consuming your own services like this has made our security better, made us finally get OAuth2 rolled out ( and finish things that have been sitting around, as we now have an app that isn’t just a 3rd party softphone, but a first class app. I forget the correct term for that! 🙂

      Oh, and how cutting edge the mobile world is and how helpful other developers are. Really pushes you. Ace fun!


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