Introduction
Voice over IP (VoIP) systems are transforming the way businesses and individuals handle communication. While cloud-based providers like Twilio and Azure offer convenient solutions, many developers and businesses are turning toward self-hosted VoIP systems for greater control, privacy, and cost savings.
In this blog post, we’ll walk you through the architecture, key components, and step-by-step guidance on how to set up a self-hosted VoIP system using modern open-source tools like Fonoster, with integration to SIP trunking, recording, and telephony infrastructure.
Why Self-Hosted VoIP?
Before diving in, here are some reasons why you might choose to self-host your VoIP platform:
- Lower ongoing costs
- Complete control over call routing, recording, and data storage
- Better integration with existing infrastructure (e.g., CRMs)
- Custom call flows and intelligent voice applications
Overview of a Self-Hosted VoIP Architecture
A typical self-hosted VoIP system consists of:
- VoIP Engine (e.g., Fonoster or Asterisk)
- SIP Trunk Provider (e.g., Telnyx, Flowroute)
- Call Routing Logic (e.g., Voice Apps in Fonoster)
- Recording and Storage (e.g., local disk, S3, MinIO)
- Database and Caching Layer (e.g., PostgreSQL, Redis)
- Frontend or Admin Interface (e.g., CRM, web portal)
Key Components Explained
1. Fonoster (VoIP Core)
Fonoster is a modern open-source programmable voice platform built on Asterisk. It abstracts telephony complexities and offers APIs similar to Twilio.
Features:
- Programmable Voice APIs
- SIP peer registration
- Voice apps (like TwiML)
- Call recording support
- Dockerized and cloud-ready
2. SIP Trunk Provider
To connect your VoIP server to the public telephone network (PSTN), you need a SIP trunk provider.
Popular options:
- Telnyx
- Twilio Elastic SIP Trunking
- VoIP.ms
- Flowroute
SIP trunk providers give you:
- Phone numbers (DIDs)
- Outbound/inbound call capabilities
- SMS (with some providers)
3. Call Routing and Logic (Voice Apps)
In Fonoster, you define Voice Apps to handle inbound and outbound calls. These are small Node.js apps that respond to events like onAnswer, onHangup, or onDTMF.
4. Recording and Storage
You can configure Fonoster to automatically record calls and store them:
- Locally on disk
- In S3-compatible storage (e.g., MinIO, Backblaze B2, AWS S3)
You can later analyze or transcribe these recordings using tools like Whisper.
5. Database (PostgreSQL) and Cache (Redis)
Fonoster uses PostgreSQL for storing metadata:
- SIP peer configurations
- Projects and users
- Call logs and usage stats
Redis is used for caching and real-time data delivery.
6. Admin Interface or Integration
You can integrate Fonoster with your existing CRM to:
- Initiate outbound calls
- Log inbound call events
- Display call history
- Link call recordings and transcripts
Final Thoughts
Running a self-hosted VoIP system gives you complete control over your communication infrastructure while reducing dependency on expensive third-party services. Tools like Fonoster make it accessible to modern developers with programmable APIs and Docker-friendly deployment.
Whether you’re building a contact center, integrating calls into your CRM, or just want to learn how VoIP works — self-hosted is a powerful option.
Resources:
- Fonoster GitHub: https://github.com/fonoster/fonoster
- Telnyx: https://telnyx.com
- Linphone (SIP Client): https://www.linphone.org/
- Zoiper (Softphone): https://www.zoiper.com/