PTT: Corporate Real-Time Communications Ecosystem
Building an instant voice Push-to-Talk system for large enterprises and distributed teams
Maksim Ermilov
WAPP founder · product & architecture
Overview
We built a mobile ecosystem for instant voice communication inside the company’s closed perimeter. The app turns Android smartphones into professional walkie-talkies, keeping teams connected over long distances with minimal latency.
Technical Challenges and Solutions
The stack is built on SIP V2.0 for session control and RTP for media. We implemented deep integration with FreeSwitch, passing commands and events directly in message headers.
A flagship feature was the “red button” for instant conference start.
Microphone Control
Using SIP INFO (DTMF), we implemented Mute/Unmute switching on the server side.
Operating Modes
The app switches between Full Duplex (while the button is pressed) and Half Duplex (receive-only).
For always-on communication the app acts as the primary phone shell:
Privileged Access
Used for boot autostart and prioritized access to system resources.
Automation
Server-initiated conference join without user action, with immediate audio on speaker.
To surface new conferences and status changes instantly, we used long polling against the API gateway—keeping the UI in sync with the SIP backend with minimal delay.
Technology Stack
- Platform: Android 12+.
- VoIP: SIP V2.0, RTP.
- Backend integration: FreeSwitch, API gateway (REST/JSON).
- Security: private VPN channels, token-based authentication.
What the Business Gains
Speed
Assemble working groups instantly with a single press.
Control
Administrators manage groups, permissions, and the corporate directory from a web console.
Reliability
The app is built as a dedicated communications tool—hard to dismiss or miss a call, unlike a casual messenger.
Client FAQ
Group settings and access rules are managed entirely from the administrative portal.
Yes—SIP telephony with a directory and dialer is part of the product.