Savenkov
Dmitriy Let’s talk
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01 / Radio communications

Interchat — HF Messaging & File Transfer

Cross-platform messaging and reliable file transfer over HF radio, with adaptive data rates and recovery from interrupted connections.

Interchat showing contacts, a conversation with ALFA1, and shared files.
Messaging and shared files in the Interchat application.View full size

Interchat is a communication application for Windows, Linux, and macOS, built for HF radio links with limited bandwidth and intermittent connectivity. I designed and implemented its communication protocol, including an application-level automatic repeat request (ARQ) mechanism that retransmits missing fragments, preserves transfer progress across application restarts and modem reconnections, and verifies completed files using SHA-256. Adaptive data-rate control adjusts transmission speed to channel conditions.

I developed the complete application, including its communication protocol, modem and transceiver integration, GPS connectivity, and a transceiver emulator for development and testing. A colleague contributed to the graphical interface; I was responsible for all other development. The application uses C++, Qt/QML, and SQLite.

Interchat transfer manager with a fragment progress map.
Transfer progress with received fragments and pause, abort and resume controls.View full size
Interchat settings with operator identity and file-transfer preferences.
Application settings for operator identity, attachments and inbox views.View full size