Java Messenger

A client/server chat application implemented in Java. The project exposes a TCP based server and a Swing desktop client that demonstrates the separation of concerns between domain logic, application use-cases, and infrastructure code.

Features

• Multi-client TCP chat server with broadcast messaging
• Swing-based client UI that renders rich message metadata
• Lightweight text protocol with base64 encoded payloads
• Clear layering with interchangeable infrastructure components
• Thorough inline documentation and architecture notes for interviews

Project Layout

See docs/ARCHITECTURE.md for a detailed overview of the package responsibilities and data flow.

src/main/java
├── com.interview.messenger.app            # Application entry points
├── com.interview.messenger.application    # Use cases and ports
├── com.interview.messenger.client         # UI + client controller
├── com.interview.messenger.domain         # Core domain model
└── com.interview.messenger.infrastructure # TCP protocol & server

Building

This project uses the standard directory layout so it can be built with any JDK (11 or newer). The following commands assume the repository root as the working directory.

# Compile all sources
javac -d out $(find src/main/java -name "*.java")

# Run the server on the default port (4444)
java -cp out com.interview.messenger.app.ServerApplication

# Run the client (requires a running server)
java -cp out com.interview.messenger.app.ClientApplication 127.0.0.1 4444 Alice

💡 Run the server in one terminal and start multiple clients (each with a unique username) in separate terminals to see message broadcasting in action.

Contributing

Improvements and alternative front-ends (CLI, web, mobile) can be added by implementing the existing ports or by introducing adapters that map to the ChatRoom use-case.