EchoLink
EchoLink connects your devices into a private mesh network and uses SSH/SFTP and TCP protocols to enable seamless clipboard sync, file transfers, and remote actions between any two online devices—keeping your data entirely off third-party clouds.
EchoLink: Zero-Cloud Device Sync
Overview
EchoLink is an open-source, decentralized device ecosystem for Windows, Linux, and Android. It delivers the seamless continuity of a unified ecosystem—sharing clipboards, transferring files, routing remote inputs, running macros, and streaming audio—without vendor lock-in or privacy-invasive cloud servers.
Built on a Reactive State Machine architecture, EchoLink tracks your devices across platforms in real-time, enforcing zero-trust connections while making cross-device interaction entirely invisible to the user.
Architecture
Building a system that connects devices across different operating systems usually requires complicated network setups and firewall exceptions. EchoLink solves this by combining power open-source networking technologies into a single, seamless pipeline:
* The Matchmaker (Headscale & Auth Middleware): You authenticate seamlessly via a self-hosted Headscale control plane control.echo-link.app) integrated with secure OIDC. A custom middleware server handles initial handshakes, allowing devices to safely introduce themselves using 6-digit PIN pairing without exposing sensitive IP addresses.
* The Secure Tunnels (Tailscale Userspace Networking): Once introduced, devices create direct, mathematically encrypted WireGuard® tunnels to each other. EchoLink embeds a Tailscale daemon running entirely in userspace (with a local SOCKS5 proxy). This bridges the devices in the background—bypassing the need for complex firewall rules, admin permissions, or system-wide VPN profiles.
* The Safety Net (DERP Relays): When strict corporate or public Wi-Fi firewalls block direct device-to-device peer connections, EchoLink automatically falls back to embedded DERP (Designated Encrypted Relay for Packets) servers. Traffic securely bounces to its destination, end-to-end encrypted, keeping devices connected anywhere.
* The Data Movers (SSH, SFTP, & Unified Protocol): With the secure tunnel established, EchoLink utilizes a multi-protocol data plane:
* SSH & SFTP (Port 44444): Battle-tested SSH handles key-exchanges (ed25519/RSA), authentication, and powers maximum-bandwidth local SFTP file transfers.
* Unified Protocol (Port 55555): A custom, low-latency TCP protocol handles real-time telemetry, clipboard broadcasting, macros, and remote-control commands instantly across the mesh.
Key Capabilities
* Universal Clipboard Sync: Instant, real-time sync with advanced modes like MirrorClip (auto-sync), SnapShare (manual push), and GhostPaste (remote apply).
* P2P File Transfer: Cloud-free file sharing driven by an internal SFTP subsystem, featuring remote directory browsing and multi-device simultaneous transfers.
* Wireless Remote Input & Control: Zero-latency PC control. Turn your Android device into a secure trackpad/keyboard, or trigger system actions (Lock, Restart, Shutdown) remotely.
* Global Macros: A centralized command center to broadcast custom scripts and automations to explicitly matched OS targets across your entire device swarm.
* Live System Monitor: Real-time cross-device telemetry logging CPU, RAM, Disk, Battery, and Thermals updated every 10 seconds over the Unified Protocol.
* Two-Way Audio Streaming: utilizing the Opus codec to stream low-latency audio across the mesh, allowing you to use your phone as a wireless PC microphone or stream PC audio directly to your mobile device.
Acknowledgments & Open Source Credits
EchoLink is made possible by the incredible work of the open-source community. This project actively utilizes and builds upon the following technologies:
* Tailscale: We bundle the Tailscale CLI binaries and userspace networking to power our zero-config WireGuard mesh network and NAT traversal. (BSD-3-Clause License)
* Headscale: Our self-hosted control plane is a customized deployment of Headscale, providing open-source, zero-cloud tenant isolation. (BSD-3-Clause License)
* Avalonia UI: Powering our responsive, cross-platform XAML interface across Windows, Linux, and Android seamlessly. (MIT License)
* SSH.NET: Driving our secure, peer-to-peer data plane, key exchanges, and SFTP file transfers. (MIT License)
* NAudio & Concentus (Opus): Handling high-performance, cross-platform audio capturing, playback, and low-latency VoIP-style encoding. (MIT License)