💬 Simple ChatSocket (Java Client–Server Chat Application)

🔗 View on GitHub

A lightweight console-based real-time chat system built using Java Sockets and Threads.
It consists of two main parts: - Server — handles client connections and message broadcasting.
- Client — connects to the server and sends/receives messages concurrently.

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🧭 Overview

This project demonstrates the fundamentals of: - Network programming with Socket and ServerSocket - Multithreading to handle multiple clients simultaneously - I/O Streams for communication between clients - Simple broadcast messaging (every client sees all messages)

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🧱 Technologies Used

• Java SE 8+
• Sockets API (java.net)
• Input/Output Streams (java.io)
• Threads (java.lang.Thread and Runnable)
• Collections Framework (ArrayList)

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🗂️ Project Structure

src/
 └── Server/
      ├── Server.java
      └── Client.java
 └── Server.iml

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🖥️ Server Side

Server.java

Handles all network connections and broadcasts messages to connected clients.

Key Responsibilities

• Opens a ServerSocket on a specified port (default: 12345)
• Accepts new client connections
• Stores all active clients’ output streams in a list
• Starts a new ClientHandler thread for each client
• Relays received messages to all clients

Example Flow

public static void main(String[] args) throws IOException {
    new Server(12345).run();
}

Console Output Example

Port 12345 is now open.
Connection established with client: 127.0.0.1
Connection established with client: 192.168.0.5

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ClientHandler.java (inner class)

Handles messages coming from each connected client.

Responsibilities: - Listens for incoming text from a single client. - Passes every message to the server for broadcasting.

@Override
public void run() {
    String message;
    Scanner sc = new Scanner(this.client);
    while (sc.hasNextLine()) {
        message = sc.nextLine();
        server.broadcastMessages(message);
    }
    sc.close();
}

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💻 Client Side

Client.java

Connects to the server and allows users to chat in real time.

How It Works

1. Connects to the server via IP and port.
2. Starts a background thread to receive messages (ReceivedMessagesHandler).
3. Prompts the user to enter a nickname.
4. Sends messages prefixed with the nickname to the server.

Socket client = new Socket(host, port);
System.out.println("Client successfully connected to server!");

Example Usage

Enter a nickname: Abdu
Send messages:
Abdu: Hello everyone!

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ReceivedMessagesHandler.java (inner class)

Runs in a background thread to continuously print messages coming from the server.

public void run() {
    Scanner s = new Scanner(server);
    while (s.hasNextLine()) {
        System.out.println(s.nextLine());
    }
    s.close();
}

This allows the client to both send and receive messages at the same time.

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⚙️ How the Chat Works

+-------------+      +------------------+      +-------------+
|   Client A  | <--> |   ServerSocket   | <--> |   Client B  |
+-------------+      +------------------+      +-------------+
        ↘                   ↕                       ↙
                Broadcast to All Clients

• Each connected client runs its own listener thread.
• The server maintains a shared list of output streams.
• Any message from one client is sent to all clients instantly.

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🚀 Running the Application

1. Compile All Files

javac Server/*.java

2. Start the Server

java Server.Server

Output:

Port 12345 is now open.

3. Start One or More Clients

Open new terminals and run:

java Server.Client

Each client will connect and start chatting instantly.

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💡 Example Chat Session

Terminal 1 (Server)

Port 12345 is now open.
Connection established with client: 127.0.0.1
Connection established with client: 127.0.0.1

Terminal 2 (Client A)

Enter a nickname: Alice
Send messages:
Alice: Hello everyone!
Bob: Hi Alice!

Terminal 3 (Client B)

Enter a nickname: Bob
Send messages:
Bob: Hi Alice!

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⚡ Core Concepts Illustrated

Concept	Description
ServerSocket	Listens for incoming TCP connections
Socket	Represents a TCP connection between client and server
Thread	Handles simultaneous clients
PrintStream	Sends text messages to clients
Scanner	Reads input from sockets
List<PrintStream>	Stores client outputs for broadcast

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🧩 Possible Improvements

• Add client disconnect detection and removal from list.
• Support for private messages (e.g., /msg username text).
• Implement GUI using Swing or JavaFX.
• Add timestamped messages.
• Encrypt messages for secure chat.

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📜 License

This project is open-source and free to use for educational purposes.