JXTA: Tech Brief

Dan Berger, Suvidhean Dhirakaosal, Essia Hamouda,

Demetris Zeinalipour CS 202 Spring 2003

Outline

Problem Statement/MotivationArchitecture OverviewExperiments/DemonstrationsConclusions

Motivation

Existing P2P solutions have had rapid adoption and success – so why build another? JXTA attempts to address 3 key “shortcomings” of typical P2P systems:

InteroperabilityPlatform IndependenceUbiquity

Interoperability

Gnutella for file sharing, ICQ/AIM/Yahoo/Jabber/MSN for instant messaging

But none of them can talk to each other.This has led to the development of apps like Gaim (linux) and Trillian (windows) that provide a single front-end to multiple protocols.

JXTA aims to standardize at the protocol level.

Platform Independence

JXTA is “independent” of programming language, operating system, and networking platform.The core of JXTA are protocol definitions, not API’s.

Ubiquity

JXTA was designed to be scalable to any device with a “network heartbeat” – cited examples are:

SensorsConsumer electronics (toasters, cell phones)PDAsEtc.

The Grand Vision

Enough Buzzwords, Already

JXTA proposes a set of services to enable building a securable logical overlay network linking “peers:”

Peer DiscoveryPeer ResolutionRendezvousPipe BindingEndpoint Routing

Gratuitous Architecture Picture

Just the Facts

Each node in the JXTA networkhas a “peer id” - a “globally” unique ID (UUID)

Urn:jxta:idform3-31:08:66:42:67:::91:24::73

Is Autonomous and may operate independently of all peers

Peers (self)organize into peer groups – loosely hierarchical.

All peers belong to the “World” group.

Peers and services are advertised with advertisements (XML documents)

Advertisements

Used to describe peers, peers groups, pipes, content, services and resourcesUsed to pass info between peersAre presented in XML

Peer Adv.Peer group Adv.Module Class Adv.Module Spec. Adv.Module Implementation Adv.

Discovery Query<xs:element name="DiscoveryQuery" type="jxta:DiscoveryQuery"/>

<xsd:simpleType name="DiscoveryQueryType"><xsd:restriction base="xsd:string">

<!-- peer --><xsd:enumeration value="0"/>

</xsd:restriction></xsd:simpleType>

<xs:complexType name="DiscoveryQuery"><xs:sequence>

<xs:element name="Type" type="jxta:DiscoveryQueryType"/><xs:element name="Threshold" type="xs:unsignedInt"

minOccurs="0"/><xs:element name="Attr" type="xs:string" minOccurs="0"/><xs:element name="Value" type="xs:string" minOccurs="0"/><!-- The following should refer to a peer adv, but is instead a whole

doc for historical reasons --><xs:element name="PeerAdv" type="xs:string" minOccurs="0"/>

</xs:sequence></xs:complexType>

Discovery

LAN-based (broadcast)Invitation (in or out of band, via an advertisement)Cascaded (controlled view across discovered peers)Rendezvous (napster-esqe)

Resolution

In general – a service that resolves advertisements into endpoints.JXTA ships with one implementation – “Rendezvous” – in which hosts serve as switchboards for messages.More complex/decentralized resolvers are possible, but not specified/provided.

Pipes

Pipes are unidirectional communication channels.Peers can host input pipes (incoming messages), or output pipes (outgoing messages).Pipes can be chained to link peers across multiple logical hops, and can be one-to-many.Pipes are bound to peer ids, not IP address.

Pipe

Routing

Allows peers to discover routes for reaching a peer which can not be directly connected to.

I.e. behind a firewall, NAT device, different network platform, etc.

Experiments

Required Components

www.jxta.org has Java and C implementations of the core protocols.

The C version is based on the APR (apache portable runtime) and trails behind the JAVA version in terms of functionality and ease of use.

For Java – requires the J2SE JDK

Installation & Configuration

Install a JRE/JDK (e.g. Sun 1.3.1_1) Download the latest JXTAInst_VM.exe InstallAnywhere installer (JXTA v2.0) http://download.jxta.org/easyinstall/install.html (4.71MB) (Or download JXTAInst.exe which contains VM)

Download tutorials/code from http://www.jxta.org/project/www/Tutorials.html

JXTA Jars

JXTA’s core uses 13 other JAR files like Jetty portable Web/Servlet Server, Log4J apache’s generic logging API. Directory Structure so far

/InstantP2P -> A “full-fledged” instant P2P application/lib -> The JAR Files

/lib/jxta.jar -> Contains the JXTA Programming API

/Shell -> Command-line Interface to JXTA/tutorials -> Tutorials that we downloaded individually

import net.jxta.peergroup.*;import net.jxta.impl.id.UUID.*;import net.jxta.impl.id.binaryID.*;

public class Hello{ static PeerGroup netPeerGroup = null; static DigestTool digestTool = new DigestTool(); public static void main(String args[]) { try { netPeerGroup = PeerGroupFactory.newNetPeerGroup(); System.out.println("Hello from JXTA group " + netPeerGroup.getPeerGroupName() ); System.out.println(" Group ID = " + netPeerGroup.getPeerGroupID().toString()); System.out.println(" Peer name = " + netPeerGroup.getPeerName()); System.out.println(" Peer ID = " + netPeerGroup.getPeerID().toString()); } catch(Exception e) { e.printStackTrace(); } }}

Step 0: Source/Compiling“Creating a PeerGroup”

java -classpath jxta.jar;OTHER_JAR_FILES.jar; Hello

Step 1 : Running the code

Now a .jxta directory is created on disk which contains all settings

On the next run we only fill in an authentication box

12

3

4

Step 2 : JXTA Sockets! (as of v2.0)

JXTA introduces a Socket API which is similar to the familiar sockets.The Socket API attempts to make JXTA Pipe programming easier. (JxtaSocket is a bi-directional Pipe)

JxtaServerSocket: Server socket that waits for connections from clients. JxtaSocket: Socket class used to create the I/O streams for both clients and servers.

Step 3 : JXTA Sockets Example

In this example we use to types of “advertisement” Discovery Services:

LAN-based discovery: Local broadcast over the subnet. (224.0.0.0 to 239.255.255.255)

Works if peers are within the same subnet or if multicast-enabled routers are connecting the peers

Discovery via rendezvous points A peer at a well-known address has the task of knowing and disseminating locations of peers.

Works if peers are fire-walled in which case direct connection between peers is not feasible.

Step 3 : JXTA Sockets Example

socket.adv<!DOCTYPE jxta:PipeAdvertisement>

<jxta:PipeAdvertisement xmlns:jxta="http://jxta.org"><Id>

urn:jxta:uuid-59616261646162614A757874614D504725184FBC</Id><Type>

JxtaUnicast</Type><Name>

socket example</Name></jxta:PipeAdvertisement>

ClientServer

read the text file1

Rendevouz Service

My ServerSocketID is uuid...BC2

read the text file3

The Server I wantto connect to isuuid...BC

4

FIREWALL

(multicast channel)

5 a)connect, b)receive msg,c) send msg back

a)connect, b)receive msg,c) send msg back

6

JXTA Sockets Code Snippets

Server (main snippets)

// create, and Start the default jxta NetPeerGroupPeerGroup netPeerGroup = PeerGroupFactory.newNetPeerGroup();

// Read file from diskFileInputStream is = new FileInputStream("socket.adv");

// Generate Pipe AdvertismentPipeAdvertisement pipeAdv = (PipeAdvertisement)AdvertisementFactory. new

Advertisement(is);

// Launch ServerSocketJxtaServerSocket serverSocket = new

JxtaServerSocket(netPeerGroup,

socEx.pipeAdv);

// if client connects, spawn two new Threads (input/output).JxtaSocket socket = serverSocket.accept();OutputStream out = socket.getOutputStream(); InputStream in = socket.getInputStream();

// send a message String msg = “Hello JXTA”;out.write(msg.getbytes());

// receive message backin.read(inbuf, 0, bufsize);

JXTA Sockets Code Snippets

Client (main snippets)

// create, and Start the default jxta NetPeerGroupPeerGroup netPeerGroup = PeerGroupFactory.newNetPeerGroup();

// Read file from diskFileInputStream is = new FileInputStream("socket.adv");

// Generate Pipe AdvertismentPipeAdvertisement pipeAdv =

(PipeAdvertisement)AdvertisementFactory. new Advertisement(is);

// Launch Socket along with 2 new Threads (input/output).JxtaSocket socket = new JxtaSocket(netPeerGroup, pipeAdv);OutputStream out = socket.getOutputStream(); InputStream in = socket.getInputStream();

// receive message read = in.read(inbuf, 0, bufsize);System.out.println(">> " + new String(inbuf));

// send message backout.write(inbuf, 0, read);

JXTA Sockets Code Snippets

Server acting also as Rendezvous

Client connecting to Rendezvous

ConclusionsJXTA Gnutella Napster Freenet/

ChordKey Difference

P2P Platform that allows the deployment of “any” P2P service

P2P Protocol tailored to the needs of file-sharers (searching based on filename

P2P Protocol tailored to the needs of file-sharers (searching based on filename)

Algorithms forObject Location in P2P systems (searching based on keys)

Architecture Any (Pure, Rendezvous (hybrid), or centralized

Pure/Hybrid P2P(started out as Pure but with Limewire’s Ultra-peers moving to Hybrid)

Centralized P2P

Structured P2P networks (peers are positioned at well-known places)

Transport HTTP or TCP/IP TCP/IP TCP/IP mostly TCP/IP

Communication

Sync/Async Asynchronous Synchronous Asynchronous

Data Replication

Open (depends on the Application)

No (downloaded file not considered replication)

No (downloaded file not considered replication)

Required

Lang Bindings

JAVA, “C”, Open source mostly in Java.

No API. (proprietary)

Java and C++

Ongoing JXTA ProjectsFull list available at : http://apps.jxta.org/servlets/ProjectHome

Gnougat: A Fully decentralized file caching

RossetChat: Localized JXTA Peer Text Messaging

Radiojxta: delivering audio content over JXTA networks

P2Pconference: A tool to conduct remote, text-based conferences

InstantP2P: To be interactively displayed.