(c) 2000 Internet Access Methods, Inc 1

Peer-To-Peer Shared Components

Gerry Seidman

IAM Consultingseidman@iamx.com

http://iamx.com212-580-2700

(c) 2000 Internet Access Methods, Inc 2

What are we doing?

Banking/Finance Commerce Design Publishing Consulting Education

(c) 2000 Internet Access Methods, Inc 3

What is the problem? Dissemination of information

– Text/images » PDF, HTML

– Reports» CGI

– Interactive » Data Entry / Analysis

(c) 2000 Internet Access Methods, Inc 4

Mechanisms of Information Presentation

Asynchronous– User works independently

» Books, reports, Web, applications, videos, tapes

Synchronous– User works with one or more other person

» In Person Classroom Consultant

» Remote Call to Call Center Direct Call to Person Conference Call Video Conference Instant Messaging

(c) 2000 Internet Access Methods, Inc 5

Relative Benefits Asynchronous

– Pros» User Paced

– Cons» Onus is on user to find solutions to any problems» No Filter of information

Synchronous– Pros

» Immediate answers

– Cons» Scheduling» All material must be present» Ability to share material» May not be the right person

(c) 2000 Internet Access Methods, Inc 6

Application Sharing

Dedicated Communication Channel– Instant Message– Shared White Board

Non-Dedicated Applications– Web– Applications– Presentations

(c) 2000 Internet Access Methods, Inc 7

Methods of Application Sharing Remote Web Control

Screen Replication over Sockets– PC-Anywhere

– Java Based

Hand Coded interactivity– A couple of 100K lines of code you can do anything

Dynamic Sharing– Java Magic

URL url = new URL("http://www.iamx.com");AppletContext ac = myApplet.getAppletContext();ac.showDocument(url);

(c) 2000 Internet Access Methods, Inc 8

Issues Behind Application Sharing

Difficulty of implementation Extensibility Performance Quality of Feedback The Voice Issue

– None– Telephone– IP Telephony

(c) 2000 Internet Access Methods, Inc 9

Development Issues

Location of Partners Data Model Location Permission Security

(c) 2000 Internet Access Methods, Inc 10

Digression on Communication Messaging

– Stream based

– Packet Based (UDP)» Inappropriate for shared applications

Connected Sockets– Requires writing a server

– Firewall Restrictions

HTTP– Connectionless

» Batch mode

– Piggyback on existing server

– Little/No Security Restrictions

(c) 2000 Internet Access Methods, Inc 11

Direct Sockets in Java Client Side

Server SideServerSocket ss = new ServerSocket(port);for(;;) {

Socket s = ss.accept();InputStream in = s.getInputStream();OutputStream out = s.getOutputStream();// process interaction, probably multithreaded

}

Socket s = new Socket(host, port);InputStream in = s.getInputStream();OutputStream out = s.getOutputStream();// process interaction, possibly multithreaded

(c) 2000 Internet Access Methods, Inc 12

HTTP Interaction from Java

URL url = new URL("http://www.iamx.com/findPartner");URLConnection connect = url.openConnection();

connect.setDoOutput(true);connect.setDoInput(true);

OutputStream out = connect.getOutputStream();// send all informationout.close();

InputStream in = connect.getInputStream();// get entire resultin.close();

(c) 2000 Internet Access Methods, Inc 13

Location of Partners

Generic Joining– No logic, maintain a list of users

Named Joining– Partner must be known– Partner must be available

Context Joining– User State determines partner

(c) 2000 Internet Access Methods, Inc 14

Context Joining Session Based

– Arbitrary amount of metric information» User ID» Location (in application)» State of Application

Matching algorithms– User Based– Current State– Past history

» Server Side State warehousing

Inversion of Call Center– Control of Call Origination

(c) 2000 Internet Access Methods, Inc 15

Implementations of Joining Algorithm

HTTP using Servlet/CGI– Piggyback on existing server– Little/No security restrictions

Direct Sockets– Only if no HTTP option is available– You only join once, so performance isn't an

issue

(c) 2000 Internet Access Methods, Inc 16

Java Shared Developer Toolkit

Messaging Framework Channel Management Session Management

http://java.sun.com/products/jsdt

(c) 2000 Internet Access Methods, Inc 17

Data Model Location

Issue:– Distributed Multithreading– VERY HARD PROBLEM!!

Implementation Options– Multiple Copies of Data Model

» Single Master

» Multi Master

– Single View Data Model Access

(c) 2000 Internet Access Methods, Inc 18

Multiple Data Model Copies

Every partner has an identical copy of the data Best solution for document based applications

– i.e., where the model is an independent entity

– Shared Word Processor

Allows for disconnect/reconnect strategies Data model synchronization is application specific

– Multi-User Diff for Word Processor Synching

(c) 2000 Internet Access Methods, Inc 19

Replicated Data Models: Single Master Mode

Only one partner can work on model at a time– Control is passed back and forth

All partners can view and notate– glass pane whiteboard, etc.

GUI for obtaining and reporting master mode ownership

(c) 2000 Internet Access Methods, Inc 20

Replicated Data Models: Multi-Master

Very hard to implement Requires rollback and user feedback for

lagged transaction clashes Not worth the bother

(c) 2000 Internet Access Methods, Inc 21

<< Demo of Shared Editor >>

(c) 2000 Internet Access Methods, Inc 22

Single Data Model Access Only one view has actual access to the data Note: Don't confuse single model with single model access

– Two partners with concurrent access to a CORBA/RMI object is NOT single partner access

– Model may be locally accessed by the partner or remote via RMI/CORBA/Sockets

Single master view into the model– Master View into Data

One (or more) Partner (Peer) Views– Views into Master View– GUI to GUI communication

View is on a Sub-Component level feedback – i.e. you see text field typing/selecting

(c) 2000 Internet Access Methods, Inc 23

<< Demo of Shared Component >>

(c) 2000 Internet Access Methods, Inc 24

Java is Great <Almost>

– You still have to rely on library implementations

Reflection– Dynamically determine object types/structure

Introspection– Dynamically inspect data– Security controlled

» private is still private

– Accessor functions safer

Object Serialization– Copying objects over streams

» Good for Models

» Bad for GUI (Ironically) Swing is not currently Serializable Model would go with GUI through Object Graph

(c) 2000 Internet Access Methods, Inc 25

Dynamic Loading and Instantiation

Dynamic Loading of classes

Dynamic Instanciation

Polymorphic UsageComponent c = (Component) x;

Object x = cl.newInstance();

Class cl = Class.forName("iam.talks.Foo");

(c) 2000 Internet Access Methods, Inc 26

Java GUI Model

Nested Container/Component Model Traversable GUI tree

Component comp = ...if (comp instanceof Container) {

Container cont = (Container) comp;Component c[] = cont.getComponents();

for(int i=0; i < c.length; i++) {// do something with c[i]

(c) 2000 Internet Access Methods, Inc 27

Security and Firewalls User access security is done at location time

– This can be reinforced by passwords and encryption

Firewall restrictions– Outward connections no problem in Browser

– Possibly a problem at the firewall

Solutions– Work behind the firewall

– Open Firewall

– Kluge a port 80 server» Frowned upon but works

– HTTP Tunnelling» You would then need a periodic or manual refresh

Yuck, but it works

(c) 2000 Internet Access Methods, Inc 28

That’s All Folks

Gerry Seidman

Internet Access Methodsseidman@iamx.com

212-580-2700

http://www.iam-there.comhttp://www.iamx.com