The Circle

See also: Distributed filesystems

Home Page:

The Circle is a peer-to-peer distributed file storage application built in Python. It is based on Chord, which is a member of the distributed hash table (DHT) algorithms.

Some of the more unusual features:

  • Most DHT don’t cope well with very common keys. The Circle has a probabilistic mechanism for sharing common keys between nodes.
  • The Circle’s chat mechanism is quite advanced: you can find people who aren’t currently online, send messages to people not currently online, send a message to a channel (IRC-style), see who on your buddy list is online. This is achieved using a combination of crypto, a distributed caching mechanism, and a clever use of the DHT.
  • All communication between peers uses UDP

Problems are:

  • The Circle does not live easily with firewalls and NAT. Firewalls need to be manually configured to accept circle packets from unknown hosts, while NAT requires a circle-specific proxy on an internet-accessible machine.

From The Circle homepage:

The Circle is a scalable decentralized peer to peer application. Which is quite a mouthful. In English, what this means is that there’s no central authority running the show. Which means no entry taxes, no one booting you off the network, and (in theory) no weak point which can break the whole system. As long is there’s one Circle peer running, anywhere in the world, there’s still a network. Circle does not try to provide anonymity, which allows it to be much more scalable than gnutella.
The Circle currently provides:
The Circle is written mainly in Python, and currenly runs on Linux, BSD and Windows, and Mac OS X. Porting it to other operating systems should not be too difficult.

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