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SyncReplacement is an FSF Priority Project. Bittorrent Sync is a peer-to-peer, two-way file synchronization utility with fine-grained access controls. We need a free software version of this client or free software that can be used for the same purpose.

If you are interested, please join this group (start by leaving your name here). We should start by surveying any existing free software that is in or close to this area (TahoeLAFS might be one), and making a list of features that are needed.

The SyncReplacement IRC channel can be found at #freesync, on Freenode.


Important News!

Recently, I posted my idea for a BTSync replacement here, below. After it was posted, I began communicating with a volunteer for the German federal disaster relief organization, THW. He wants to potentially use this program in connection with their disaster relief efforts, but he needs it to have additional functionality, including the ability to synchronize between more than two computers and the ability to do block-level synchronization. I have been trying to add that functionality, but it obviously takes a good deal of time to do so, and more than I currently have. Additionally, I need multiple computers to test the latest version, a resource which I do not have. Would anyone be interested in working with me to add some of this functionality to the program and help test the program? If so, please let me know. You can contact me at jhunter (dot) dunefsky (at) gmail (dot) com.

Thanks Hunter D

Existing Solutions

We need a survey of existing solutions, their features, pros, and cons.

In development

Currently there's a protocol description implemented by Jewel in a ruby client:

And there's an effort to create a portable C++ daemon for the clearskies protocol:


Hive2Hive is an open-source library, written in Java, for distributed, P2P-based file synchronization and sharing. It provides a free, distributed solution that focuses on maximum security and privacy of both users and data. It supports the whole feature set known from similar centralized approaches, such as Dropbox or Google Drive, all packed in a clean, extendable API. On top of that, it has several other advantages that are described on their website. The project is hosted on GitHub:


Under active development in Go, syncthing claims to be an "Open Source Continuous File Synchronization" solution. It specifies a protocol Block Exchange Protocol and a reference implementation. Syncthing is released under the GPLv3 license.



The software that lit a fire under this project.


A DropBox competitor that offers peer to peer file sync called 'DirectSync'.


This section might need pruning, the things listed might not be entirely free.


A decentralised communication platform that allows file sharing.

peer discovery with DHT
NAT traversal
encryption and authentication with PGP+OpenSSL
gui to manage friends+groups
additional functionality like chat, groupchat, voip... I think it is nice to have chat and shared folders at the same place. This would enable fast collaboration.
Retroshares core "libretroshare" is written in C++, and runs on every platform with sockets and a file system
Retroshare-gui uses Qt and runs on win, linux, mac
Plugins can use the secure link to send/receive data to/from peers.
Resumable transfers and swarming
no worry about finding peers or securing the connection
Retroshare has a community of developers, testers, translaters and packers. So we could concentrate on the main thing: how to get different states of a folder in sync.
Perhaps this does too much? We want a drop in replacement for BTSync, this comes with a whole raft of additional features that might not appeal to users.








Our Solution



The Protocol

for every shared folder we have:

(set by admin, so update is simple with timestamp)

created by users with permissions:

file metadata item:

How sync works:

  1. file metadata items are exchanged, so everyone has the same list
  2. fileitems with same path/name are ordered, so that we know the newest state of the file
  3. files are transferred

Conflicts need to be handled by the user

More thoughts


Here's a list of people that have volunteered to be a part of this project so far. Feel free to add yourself to this list.

Gittorrent seems dead. contact me at tobias [ät] platen-software [döt] de

I have experience with Java, Python and C. I learn C++ and Qt.

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