COMP90015 Project 2 – Extended Multi-Server Chat System solution


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1. Synopsis
This assignment is to extend the Multi-Server Chat System in the assignment 1. The project primarily focuses
on addressing the following challenges of the system:
• Security
• Failure
• Scalability
Moreover, this project should be demonstrated using Virtual Machines (VMs) running in the Cloud
environment. More details can be found in the later part of the description.
Optionally you can design and implement a Graphical User Interface (GUI) for the Chat Client. Extra
points for this part will be awarded. The source code of the chat client program with Command Line
Interface (CLI), used in the previous assignment, will be shared with you.
In this assignment you have the freedom to design and implement your own protocols and to add new
components to the previous project.
This is a group assignment. You need to make a group of 3 or 4 people.
In the following sections we provide requirements regarding each of the above.
2. Security
To address security at least three main issues must be addressed.
1) All communications (between servers and between clients and servers) in the system should be happening
via secure channels (encrypted communication).
• Recommendation: Use TSL/SSL TCP connections with self-signed certificates.
2) You need to provide an authentication mechanism for your project. Only registered and authorized users
with valid username and password can log in into the system (No need to impelement a registration method.
This can be manual.)
• Recommendation: Create a central authentication server with some predefined users.
Extra 5 points will be awarded if you can enable authentication using OAuth2 protocol with Facebook, Google
or Twitter accounts. This is only recommended to those who have good programming skills.
3) You need to add the authentication feature to the given chat client program to support your authentication
2. Security 1
Note that chat servers only allow connections for authorized clients passing the authentication phase.
The username is not necessarily the same as client identity. For example my username might be or anadjaran and my chat client id is adel.
3. Failure Handling
Your project should address the following failure:
If a chat server crashes or stops responding, other chat servers should detect this situation. All chatrooms on
that server should be removed from the list and clients should not be redirected to that server anymore.
Recommendation: Use heartbeat signals generated at regular intervals to check if the other servers
are working correctly.

You do not need to handle failures for the chat clients. Clients are simply getting disconnected in the case of a
chat server crash. The chatrooms and other data associated to the user will be deleted in a similar way to the
previous project.
4. Scalability
For the sake of scalability, your system has this feature that the system admin can add new servers to the
system manually.
The newly added servers become fully functional components of the chat system and clients can directly
connect to these chat servers. Thus, these servers participate in all the Lock and Release communications
among chat servers to handle client identities and chat rooms.
Recommendation: Add new JSON messages to the communication protocol of servers to support
this feature that a new server can introduce itself to the system.

5. A Chat client program with GUI
Design and implement a chat client program with a GUI.
Please note that creating chat client with GUI is optional. You will receive extra 10 marks (100 + 10) for
addressing the requirements of this section.
Source code for the chat client program used in the previous assignment will be shared with you as a sample.
You can reuse the code or develop your own code from scratch. If you decide to implement your own chat
client, you can use the programming language of your choice for this purpose.
The chat client should support all the features of the previous project plus the authentication.
5. A Chat client program with GUI 2
6. Demo
You have to demonstrate the project. For the demo purpose you need to use an Infrastructure-as-a-Service
(IaaS) Cloud to run your chat servers on multiple VMs.
Recommendation: Use Nectar or alternative cloud services to host your Chat Servers and run the

More details about Nectar Cloud will be given in the tutorials.
7. Your Report
Use 10pt font, double column, 1 inch margin all around. Put the names of all the group members, as well as
their university username, and student number at the top of your report.
In up to 1500 words discuss:
• The overall architectural model of you application (use diagrams).
How did you implement the communications between components of the system? Use UML
Sequence diagrams to illustrate the main communication patterns.

• Technologies did you use and why?
Which functionality did each one of the team complete? You will be asked specific questions based
on that.

Note that you will receive marks based on your contributions to the project. You should be familiar with all
the components of the project even if you take care of only one of the required features. Just preparing the
report is not enough contribution for a member of the team to pass the assignment.
• Recommendation: It is strongly recommended that the report is prepared by all team members.
8. Submission
You need to submit the following via LMS:
• Your report in PDF format only.
• Your source and executable files in a .ZIP archive only.
Submissions will be due on Wednesday 19th of October 11:59pm.
This is a hard deadline that will not be extended as the week after is SWOT Vac. Demo time, date, and place
for each group will be arranged on the 20th and 21st of October and will be announced close to the
submission date.
8. Submission 3