EchoLink

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, and routing remote inputs - without vendor lock-in or privacy-invasive cloud servers.

Architecture

Building a system that connects devices across different operating systems usually requires complicated network setups. EchoLink makes this invisible to the user by combining four powerful open-source technologies:

• The Matchmaker (Headscale): You host a lightweight central server. This server never sees or stores your files; it simply authenticates your devices and securely introduces them to each other over the internet.

• The Secure Tunnels (Tailscale & WireGuard): Once introduced, your devices create direct, mathematically encrypted tunnels to each other. By embedding Tailscale’s tsnet directly into the EchoLink app, this happens entirely in the background—bypassing the need for complex firewall rules or system-wide VPN permissions.

• The Safety Net (DERP Relays): Sometimes, strict corporate or public Wi-Fi firewalls block direct device-to-device connections. When this happens, EchoLink automatically falls back to an embedded DERP (Designated Encrypted Relay for Packets) server. This relay securely bounces your encrypted traffic to its destination without ever being able to read it, guaranteeing your devices stay connected anywhere.

• The Data Movers (SSH & SFTP): With the secure tunnel established, EchoLink uses battle-tested SSH and SFTP protocols to actually move your data. Because the devices have permanent, private IP addresses, data travels at the absolute maximum speed of your local Wi-Fi router.

Key Capabilities

• Universal Clipboard Sync: Instant, real-time text and link syncing across the mesh.

• P2P File Transfer: Cloud-free file sharing driven by an internal SFTP subsystem that maximizes local network bandwidth.

• Wireless Remote Input: Zero-latency PC control using a continuous SSH data stream, instantly turning an Android device into a secure trackpad and keyboard.

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 (https://github.com/tailscale/tailscale): We bundle the Tailscale CLI binaries and embed the tsnet library to power our zero-config WireGuard mesh network and NAT traversal. (BSD-3-Clause License)

• Headscale (https://github.com/juanfont/headscale): Our self-hosted control plane is a customized deployment of Headscale, providing open-source, zero-cloud tenant isolation. (BSD-3-Clause License)

• OpenSSH (https://github.com/juanfont/headscale): We utilize OpenSSH binaries and the golang.org/x/crypto/ssh package to drive our secure, peer-to-peer data plane and SFTP file transfers.