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JXTA: Tech Brief
Dan Berger, Suvidhean
Dhirakaosal, Essia Hamouda,
Demetris Zeinalipour
CS 202 Spring 2003
Outline
Problem Statement/Motivation
Architecture Overview
Experiments/Demonstrations
Conclusions
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
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:
Sensors
Consumer electronics (toasters, cell
phones)
PDAs
Etc.
The Grand Vision
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
Gratuitous Architecture Picture
Just the Facts
Each node in the JXTA network
has 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 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.
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
Step 0: Source/Compiling
“Creating a PeerGroup”
java -classpath jxta.jar;OTHER_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.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 1 : Running the code
1
Now a .jxta directory is created on disk which contains all settings
3
4
On the next run we only fill in an authentication box
2
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 bidirectional 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 multicastenabled routers are connecting the peers
Discovery via rendezvous points A peer at a wellknown 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
Rendevouz Service
Server
FIREWALL
5
My ServerSocket
2 ID is uuid...BC
a)connect, b)receive msg,
c) send msg back
(multicast channel)
1 read the text file
6
a)connect, b)receive msg,
c) send msg back
Client
4 The Server I want
to connect to is
uuid...BC
3 read the text file
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>
JXTA Sockets Code Snippets
Server (main snippets)
// create, and Start the default jxta NetPeerGroup
PeerGroup netPeerGroup = PeerGroupFactory.newNetPeerGroup();
// Read file from disk
FileInputStream is = new FileInputStream("socket.adv");
// Generate Pipe Advertisment
PipeAdvertisement pipeAdv = (PipeAdvertisement)AdvertisementFactory. 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();
// send a message
String msg = “Hello JXTA”;
out.write(msg.getbytes());
// receive message back
in.read(inbuf, 0, bufsize);
JXTA Sockets Code Snippets
Client (main snippets)
// create, and Start the default jxta NetPeerGroup
PeerGroup netPeerGroup = PeerGroupFactory.newNetPeerGroup();
// Read file from disk
FileInputStream is = new FileInputStream("socket.adv");
// 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);
System.out.println(">> " + new String(inbuf));
// send message back
out.write(inbuf, 0, read);
JXTA Sockets Code Snippets
Server acting also
as Rendezvous
Client connecting
to Rendezvous
Conclusions
JXTA
Gnutella
Napster
Freenet/Chord
Key Difference
P2P Platform that
allows the
deployment of
“any” P2P service
P2P Protocol
tailored to the
needs of filesharers (searching
based on filename
P2P Protocol
tailored to the
needs of filesharers
(searching based
on filename)
Algorithms for
Object 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 Projects
Full 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.