Syncthing

Technology

Syncthing is written in Go and implements its own, equally free Block Exchange Protocol.

Syncthing is a BYO cloud model where the users provide the hardware the software runs on. It works generally in the same way that Resilio Sync does where the larger the number of mesh devices, the more efficiently data can be transferred. It supports IPv6 and, for those on IPv4 networks, NAT punching and relaying are offered. Devices connecting to each other require explicit approval (unless using the Introducer feature) which increases the security of the mesh. All data, whether transferred directly between devices or via relays, is encrypted using TLS.

Conflicts are handled with the older file being renamed with a "sync-conflict" suffix (along with time and date stamp), enabling the user to decide how to manage two or more files of the same name that have been changed between syncing. GUI Wrappers can use these files to present the user with a method of resolving conflicts without having to resort to manual file handling.

Efficient syncing is achieved via compression of metadata or all transfer data, block re-use and lightweight scanning for changed files, once a full hash has been computed and saved. Syncthing offers a "Master Folder" feature where updates from remote devices are not processed, various types of file versioning (trash can, simple or staggered versioning as well as handing versioning to an external program or script) and file/path ignore patterns. Two different SHA256 hashing algorithms are currently supported, the faster of which will be used dynamically after a brief benchmark on start-up. Moving and renaming of files and folders is handled efficiently, with Syncthing intelligently processing these operations rather than re-downloading data from scratch.

Infrastructure

Device discovery is achieved via publicly-accessible discovery servers hosted by the project developers, local (LAN) discovery via broadcast messages, device history and static host name/addressing. The project also provides the Syncthing Discovery Server program for hosting one's own discovery servers, which can be used alongside, or as a replacement of the public servers.

The network of community-contributed relay servers allows devices that are both behind different IPv4 NAT firewalls to be able to communicate by relaying encrypted data via a third party. The relaying performed is similar in nature to the TURN protocol, with the traffic TLS-encrypted end-to-end between devices (thus even the relay server cannot see the data, only the encrypted stream). Private relays can also be set up and configured, with or without public relays, if desired. Syncthing will automatically switch from relaying to direct device-to-device connections if it discovers that a direct connection has become available.

Syncthing can be used without any connection to the project or community's servers: upgrades, opt-in usage data, discovery and relaying can all be disabled and/or configured independently, thus the mesh and its infrastructure can all be run in a closed system for privacy or confidentiality.

Configuration and Management

Syncthing can be configured via a web UI locally or remotely (and supports access via proxy server), the REST and Events APIs or one of the community-contributed wrapper programs. Links to Docker images are also provided on the community contributions page, as well as links to supported configuration management solutions such as Puppet, Ansible and others.

Reception

History

The initial public binary release (v0.2) was made on 30 December 2013.

In October 2014 it was announced by the original author that Syncthing was being rebranded as "Pulse". However, on November 17, the developer decided not to change Syncthing to Pulse and is no longer working with ind.ie. Ind.ie's Pulse is now an officially sanctioned fork of Syncthing.