P2P

In my implementation I preferred to put all Chord's business logic in three objects:

1. Node,
2. ChordId,
3. FingerTable

then I decided to delegate all communication and stabilization task to four other components (which are objects in Picocontainer's language)

1. HubManager,
2. ServerManager,
3. TaskManager,
4. StabilizationManager.

More in deep:

1. ChorId contains all "arithmeticians" methods according to Chord's clockwise mathematics. Specially "belongs", "belongsLeftInclusive" and "belongsRightInclusive" which implement respective x € (a,b), x € [a,b) and x € (a,b].
   
2. Node contains all Chord specific methods among which "join", "leave", "findSuccessor", etc. according to Chord protocol specification document and also it holds FingerTable object.
   
3. HubManager holds the Node object and it is delegated by Node to start comunication tasks to find remote information. It creates messages to be send to remote nodes whose pointer is a NodeHandle object. HubManager starts up Node and creates, when it is delegated by Node object, a message and a listener to be pushed in a stack. Each message has a unique key, the same key is assigned to a listener which is used as entry poing to a callback function. Messages are "poped" from stack by TaskManager who does the "hard work" of communication. Listeners are used to handle response from remote node.
   
4. TaskManager and ServerManager do the actual communication. Modifying these two components we can implement an in-process chord network maybe for simulation purposes.
   
5. StabilizationManager manages stabilization jobs using Quartz Scheduler facilities. Each stabilization job delegates HubManager to create messages and listeners to stabilize the network.
   

More on Chord and Accord project which is were to find code is here

I made an imlplementation of Chord protocol it can be found here in CVS repository
Here is a brief explanation of code: there are two subprojects one named site and one named hub.

Site project is a site to be used as a registry where every Chord node says "I'm alive!".
I used this approach because I needed a dinamic way to find "the known node" to be used for join method at node's bootstrap.
Site is build onto Springframework and it keeps an in-memory registry of alive nodes. At moment it has no way to know is a node is down. Nodes communicate with site via XML on HTTP.

Hub project is the actual implementation of Chord protocol.
I wanted to concentrate on chord protocol so I used some open source framework and toolkit for common tasks.
Hub lifecycle is managed throught Picocontainer , an IOC framework.
Stabilization tasks are scheduled by Quartz scheduler; HTTP comunication is made by Jakarta HTTP commons client, logging is delegated to Log4j and administration is made using JMX and MX4J.

I'm looking at techologies dealing with P2P. I found Chord.

The Chord project aims to build scalable, robust distributed systems using peer-to-peer ideas.

Chord is basically a distributed lookup system it is completely decentralized and symmetric, and can find data using only log(N) messages, where N is the number of nodes in the system. So I found it: Chord is the overlay building block I needed to make up a network of peers! To have more infos about Chord look here otherwise stay connected "furthers" will come... Marco.