The developer created three open-source projects to manage SMS and telephony using personal hardware, avoiding third-party subscription fees and data storage. The suite includes SMSNodeBackend, a server for GSM gateways; SMSNode, a Kotlin Multiplatform client; and SIPgram, a gateway connecting FreePBX to Telegram.
SMSNodeBackend is built on Python, FastAPI, and PostgreSQL, supporting GoIP and Skyline gateways. It handles SMS queues, throttling, and multi-user access. The system uses UDP, HTTP, or SMTP to communicate with gateways. The developer implemented a custom protocol to manage SMS, USSD, and device settings, noting that port identification relies on source IP addresses.
The SMSNode client uses Kotlin Multiplatform and Compose Multiplatform to provide a unified interface across Android, iOS, Windows, macOS, Linux, and web browsers. It uses a polling mechanism rather than WebSockets for stability. The application is available in major app stores and includes a mock mode for testing without physical hardware.
SIPgram functions as a SIP-to-Telegram gateway, allowing internal PBX extensions to receive and make calls via Telegram. It uses the NTgCalls library and a custom SIP stack written in Python. The system supports standard office phone features, including DTMF, call holding, transfers, and conference calls, while keeping routing and recording logic on the PBX side.
The developer notes that SIPgram allows a single Telegram account to handle multiple simultaneous calls for different users. The project includes features like click-to-call via HTTP API and scheduling for quiet hours. Future plans include replacing the internal process queue with RabbitMQ or Redis Streams and implementing push notifications.
