JXTA: Tech Brief

1
JXTA Tech Brief

• Dan Berger, Suvidhean Dhirakaosal, Essia Hamouda,
  Demetris Zeinalipour
• CS 202 Spring 2003

2
Outline

• Problem Statement/Motivation
• Architecture Overview
• Experiments/Demonstrations
• Conclusions

3
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
• Interoperability
• Platform Independence
• Ubiquity

4
Interoperability

• Gnutella for file sharing, ICQ/AIM/Yahoo/Jabber/MS
  N 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.

5
Platform Independence

• JXTA is independent of programming language,
  operating system, and networking platform.
• The core of JXTA are protocol definitions, not
  APIs.

6
Ubiquity

• JXTA was designed to be scalable to any device
  with a network heartbeat cited examples are
• Sensors
• Consumer electronics (toasters, cell phones)
• PDAs
• Etc.

7
The Grand Vision
8
Enough Buzzwords, Already

• JXTA proposes a set of services to enable
  building a securable logical overlay network
  linking peers
• Peer Discovery
• Peer Resolution
• Rendezvous
• Pipe Binding
• Endpoint Routing

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Gratuitous Architecture Picture
10
Just the Facts

• Each node in the JXTA network
• has a peer id - a globally unique ID (UUID)
• Urnjxtaidform3-3108664267912473
• 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)

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Advertisements

• Used to describe peers, peers groups, pipes,
  content, services and resources
• Used to pass info between peers
• Are presented in XML
• Peer Adv.
• Peer group Adv.
• Module Class Adv.
• Module Spec. Adv.
• Module Implementation Adv.

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Discovery Query

• ltxselement name"DiscoveryQuery"
  type"jxtaDiscoveryQuery"/gt
• ltxsdsimpleType name"DiscoveryQueryType"gt
• ltxsdrestriction base"xsdstring"gt
• lt!-- peer --gt
• ltxsdenumeration value"0"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• ltxscomplexType name"DiscoveryQuery"gt
• ltxssequencegt
• ltxselement name"Type" type"jxtaDiscoveryQuer
  yType"/gt
• ltxselement name"Threshold" type"xsunsignedIn
  t" minOccurs"0"/gt
• ltxselement name"Attr" type"xsstring"
  minOccurs"0"/gt
• ltxselement name"Value" type"xsstring"
  minOccurs"0"/gt
• lt!-- The following should refer to a peer adv,
  but is instead a whole doc for historical reasons
  --gt
• ltxselement name"PeerAdv" type"xsstring"
  minOccurs"0"/gt
• lt/xssequencegt
• lt/xscomplexTypegt

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Discovery

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

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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.

15
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.

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Pipe
17
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.

18
Experiments
19
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

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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.ht
  ml (4.71MB)
• (Or download JXTAInst.exe which contains VM)
• Download tutorials/code from
• http//www.jxta.org/project/www/Tutorials.htm
  l

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JXTA Jars

• JXTAs core uses 13 other JAR files like Jetty
  portable Web/Servlet Server, Log4J apaches
  generic logging API.
• Directory Structure so far
• /InstantP2P -gt A full-fledged instant P2P
  application
• /lib -gt The JAR Files
• /lib/jxta.jar -gt Contains the JXTA Programming
  API
• /Shell -gt Command-line Interface to JXTA
• /tutorials -gt Tutorials that we downloaded
  individually

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Step 0 Source/CompilingCreating a PeerGroup
java -classpath jxta.jarOTHER_JAR_FILES.jar
Hello
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.newNetPee
rGroup() 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()

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Step 1 Running the code
1
2
Now a .jxta directory is created on disk which
contains all settings On the next run we
only fill in an authentication box
3
4
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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.

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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.

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Step 3 JXTA Sockets Example
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JXTA Sockets Code Snippets

• Server (main snippets)
• // create, and Start the default jxta
  NetPeerGroup
• PeerGroup netPeerGroup PeerGroupFactory.newNetPe
  erGroup()
• // Read file from disk
• FileInputStream is new FileInputStream("socket.a
  dv")
• // Generate Pipe Advertisment
• PipeAdvertisement pipeAdv (PipeAdvertisement)Adv
  ertisementFactory. new Advertisement(is)
• // Launch ServerSocket
• JxtaServerSocket 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()

// receive message back in.read(inbuf, 0,
bufsize)
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JXTA Sockets Code Snippets

• Client (main snippets)
• // create, and Start the default jxta
  NetPeerGroup
• PeerGroup netPeerGroup PeerGroupFactory.newNetPe
  erGroup()
• // Read file from disk
• FileInputStream is new FileInputStream("socket.a
  dv")
• // Generate Pipe Advertisment
• PipeAdvertisement 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)

// send message back out.write(inbuf, 0, read)
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JXTA Sockets Code Snippets
Server acting also as Rendezvous
Client connecting to Rendezvous
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Conclusions
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Ongoing JXTA Projects
Full list available at http//apps.jxta.org/serv
lets/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 InstantP
2P To be interactively displayed.