💬 Chat Server — Java Sockets

A multi-client TCP chat server built with Java Sockets and multithreading.

Homework project for the Sockets & Multithreading lesson at AIT TR GmbH (cohort 60).

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📋 Task

Implement the run() method in ChatServerReceiver to get the main chat server logic working:

• Each connected client gets its own ChatServerReceiver thread that reads incoming messages
• Messages are prefixed with the sender's IP address and port, then placed into a shared BlockingQueue
• ChatServerSender broadcasts each message to all connected clients except the sender

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🛠 Tech Stack

• Java
• Java Sockets (ServerSocket, Socket)
• Multithreading (Runnable, Thread)
• BlockingQueue (thread-safe message passing)
• BufferedReader / PrintWriter for stream I/O

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🏗 Architecture

                    ┌─────────────────────────────┐
                    │        Chat Server           │
                    │                              │
  Client A ──────► │  ChatServerReceiver (Thread) │
                    │         ↓ messageBox         │
  Client B ──────► │  ChatServerReceiver (Thread) │ ──► ChatServerSender (Thread) ──► all clients except sender
                    │         ↓ messageBox         │
  Client C ──────► │  ChatServerReceiver (Thread) │
                    └─────────────────────────────┘

Each new client connection spawns:

• 1 ChatServerReceiver thread — reads messages from the client socket
• The shared ChatServerSender thread — broadcasts messages to all other clients

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🔑 Key Implementation Details

ChatServerReceiver.run() — the core homework task:

String message = socketReader.readLine();
message = String.format("%s:%s|%s", socket.getInetAddress(), socket.getPort(), message);
messageBox.add(message);

Messages are tagged with ip:port so the sender can be identified and excluded from broadcast.

ChatServerSender.run() — broadcasts to all except sender:

String fullMessage = messageBox.take();       // blocking — waits for a message
String[] parts = fullMessage.split("\\|", 2);
String name = parts[0];                       // sender's ip:port
String message = parts[1];                   // actual message text
clients.stream()
    .filter(client -> !client.getName().equals(name))
    .forEach(client -> client.getWriter().println(message));

Client model — wraps a PrintWriter and the client's ip:port name for identification.

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📁 Project Structure

src/ait/chat/server/
├── model/
│   └── Client.java              # Holds PrintWriter + client name (ip:port)
└── task/
    ├── ChatServerReceiver.java  # Runnable — reads messages from one client socket
    └── ChatServerSender.java    # Runnable — broadcasts messages to all other clients

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🚀 Getting Started

git clone https://github.com/AOgit/ait-chat-socket_server.git
cd ait-chat-socket_server

Open in IntelliJ IDEA and run the main server class.
Connect multiple clients using telnet or a matching socket client:

telnet localhost <port>