HACOGroupChat

A highly available, causally ordered group chat for the Distributed Systems course A.Y. 2023/2024.

Implement a distributed group chat application.
Users can create and delete rooms. For each room, the set of participants is specified at creation time and is never modified.
Users can post new messages for a room they are participating to.
Within each room, messages should be delivered in causal order.
The application should be fully distributed, meaning that user clients should exchange messages without relying on any centralized server.
The application should be highly available, meaning that users should be able to use the chat (read and write messages) even if they are temporarily disconnected from the network.
The project can be implemented as a real distributed application (for example, in Java) or it can be simulated using OmNet++.

Assumptions
• Clients are reliable but they can join and leave the network at any time. Network failures and partitions may happen.

Our assumptions
• The Discovery server node is always reachable by all peers.
• Message packets are not bigger than 2000 bytes each.

The pdf of the spec is available here.

We chose to implement the application with a real distributed application using Java.

Running the jars

The application requires an installation of Java 21. Newer versions cannot be used as preview features were used which may have been changed in Java 22.

The jars can be found in the releases section.

The discovery server needs to be run from terminal using the following command:

java --enable-preview -jar HACOGroupChat-discovery-2.0.jar

The distributed application needs to be run from terminal using the following command:

java --enable-preview -jar HACOGroupChat-peer-2.0.jar

Running with the embedded JRE

Other than the jars, zipped archive are also included for the supported platforms (Windows amd64, MacOS aarch64 and Linux amd64, see README) which also contain an embedded JRE. These can be run by executing, respectively:

• bin/peer-console.sh and bin/discovery.sh for *NIX
• bin/peer.bat, bin/peer-console.bat and bin/discovery.bat for Windows