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Distributed System and Application
Cloud Computing and Distributed Systems (CLOUDS) Laboratory
School of Computing and Information Systems
The University of Melbourne, Australia
Other contributors: All Tutors
Project: Distributed Shared White Board
In these slides, we are offering mainly guidelines for satisfactory
work, but be innovative and creative, which will be valued a lot.
Team/Members Size: 1 – Individual (like Assignment 1).
General help: Ask your tutor during/after tutorial session. Also
use “Discussion Board” in LMS.
Marks Allocated: 25
Note: We expect all students to just finish and submit only the
features noted in this specification.
To help you in planning, we propose:
Basic Features (first complete a system with these features as they are
easier to implement)
Shared White Board – Distributed Users
Shared whiteboards allow multiple users to draw simultaneously on a
canvas. There are multiple examples found on the Internet that
support a range of features such as freehand drawing with the
mouse, drawing lines and shapes such as circles and squares that
can be moved and resized, and inserting text.
Dealing with concurrency
Regardless of the technology you use, you will have to ensure that access to
shared resources is properly handled and that simultaneous actions lead to a
Structuring your application and handling the system state
For example, you can have multiple servers that communicate with each other or
a single central one that manages all the system state.
Dealing with networked communication
You need to decide when/what messages are sent across the network.
You may have to design an exchange protocol that establishes which messages
are sent in which situation and the replies that they should generate.
If you use RMI, then you need to design your remote interface(s) and servants
Implementing the GUI.
The functionality can resemble tools like MS Paint.
You can use any tool/API/library you want.
e.g.: Java2D drawing package
Distributed White Board
Develop a white board that can be shared between multiple users
over the network.
The system must be implemented in Java, but you can choose
the technology (e.g., it can be even Sockets) you want to use to
build your distributed application:
TCP or UDP?
Message format and Exchange protocol? can be XML-based or your own format)
Client can broadcast a message with updates to all other clients, other clients reply acknowledging the
Remote Objects/Remote Interface?
File or Database for Storage
Please Choose any technology of your choice
Make sure that can achieve the goal when you are choosing “new”
technology (otherwise, stick to what you already know).
Requirements 1: Basic Features
Whiteboard – Multiuser system
Multiple users can draw on a shared interactive canvas.
Your system will support a single whiteboard that is shared between all
of the clients.
Key Elements with GUI
Shapes: at least your white board should support for line, circle, oval, and rectangle.
Text inputting– allow user to type text anywhere inside the white board.
User should be able choose their favourite colour to draw the above features. At least 16
colours should be available.
Of course, you are most welcome to be creative/innovative.
Requirements 2: Advanced Features
1. Chat Window (text based): To allow users to
communicate with each other by typing a text.
2. A “File” menu with new, open, save, saveAs and
close should be provided (only the manager can
3. Allow the manager to kick out a certain
Guidelines on Usage/Operation
Users must provide a username when joining the whiteboard. There should
be a way of uniquely identifying users, either by enforcing unique usernames
or automatically generating a unique identifier and associating it with each
All the users should see the same image of the whiteboard and should have
the privilege of doing all the drawing operations.
When displaying a whiteboard, the client user interface should show the
usernames of other users who are currently editing the same whiteboard.
Clients may connect and disconnect at any time. When a new client joins the
system, the client should obtain the current state of the whiteboard so that
the same objects are always displayed to every active client.
Only the manager of the whiteboard should be allowed to create a new
whiteboard, open a previously saved one, save the current one, and close
Users should be able to work on a drawing together in real time, without
appreciable delays between making and observing edits.
Proposed Startup/Operational Model
The first user creates a whiteboard and becomes the whiteboard’s
Other users can ask to join the whiteboard application any time by
inputting server’s IP address and port number
A notification will be delivered to the manager if any peer wants to
join. The peer can join in only after the manager approves
A dialog showing “someone wants to share your whiteboard”.
An online peer list should be maintained and displayed
All the peers will see the identical image of the whiteboard, as well as
have the privilege of doing all the operations.
Online peers can choose to leave whenever they want. The manager
can kick someone out at any time.
When the manager quits, the application will be terminated. All the
peers will get a message notifying them.
Guidelines/Suggestions for Implementation
These phases are suggestions for timely progression,
you are most welcome to follow your own approach.
Phase 1 (whiteboard) – (aim to finish within 2 weeks of
As a starting point: Single-user standalone whiteboard (OR)
You are most welcome to implement a single user and single
Task A: Implement a client that allows a user to draw all the
Task B: Implement a server so that client and server are able to
communicate entities created in Task A
Guidelines/Suggestions for Implementation
Phase 2 (user management skeleton)
Allow the manager to create a whiteboard
Allow other peers to connect and join in by getting approval from
Allow the manager to choose whether a peer can join in
join in means the peer's name will appear in the user list
Allow the joined peer to choose quit
Allow the manager to close the application, and all peers get
Allow the manager to kick out a certain peer/user
Guidelines – Suggestions (You are most
welcome follow your own approach)
Phases 3 (Final)
Integrate the whiteboard with the user
management skeleton (phases 1 and 2)
What communication mechanism will be used?
Socket, RMI, or any other frameworks of your choice.
How to propagate the modification from one peer to
You may need an event-based mechanism
How many threads do we need per peer?
At least one for drawing, one for messaging
Deliverables and Marks
Report (4 marks)
Code and Demo of Network-based
Distributed Users, Shared Whiteboard:
Basic System (16 marks)
Advanced Features (5 marks)
FAQ (Frequently Asked Question)
Can I submit without competing Advanced Features?
Yes, you can. But you will NOT get associated marks!
NOTE: You are NOT allowed to use ANY code taken from any
existing shared whiteboard implementation. Full design, code,
report has to be Your OWN work. Copying code/content from
other sources carries penalty & disciplinary action as per the
You should write a report that includes the system architecture,
communication protocols and message formats, design diagrams
(class and interaction), implementation details, new innovations
Don’t document anything you haven’t implemented in the report.
This is misconduct and will result in severe penalties.
You need to submit the following via LMS:
Your report in PDF format only.
The executable jar files used to run your system’s
Your source files in a .ZIP or .TAR archive only.
You will showcase your system and discuss your design choices
during the demos.
Date and venue will be announced closer to the submission date.
Deadline and Penalties
May 25, 2023 (Thursday) at 5:00pm
Assignments submitted late will be penalized
in the following way:
1 day late: -1 mark
2 days late: -2 marks
3 days late: -3 marks
4 days late: -4 marks
etc. (that is, -1 mark for each day delay).