Single Client Chat & Multiple Client Chat Connection

In Java, a single-client chat connection typically involves a server and one client, where the server waits for the client's messages and responds accordingly. This setup uses ServerSocket to listen for connections and Socket to handle communication. For multiple-client chat connections, the server needs to handle simultaneous interactions with multiple clients. This is achieved through multithreading, where each client connection is managed by a separate thread. The server continues to use ServerSocket to accept connections, while each client's communication is handled in an individual Thread using Socket. This approach ensures that the server can maintain concurrent conversations with multiple clients, enabling a robust and scalable chat application.

Author: JASJOTSINGH08

Client Connection/1.jpg

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+import java.io.*;
+import java.net.*;
+
+public class MultiClient {
+    private static final String SERVER_ADDRESS = "localhost"; // Change this to the server's IP address if it's not
+                                                              // localhost
+    private static final int SERVER_PORT = 1234;
+
+    public static void main(String[] args) {
+        try (Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT);
+                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
+                PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
+                BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in))) {
+
+            System.out.println("Connected to server: " + socket.getRemoteSocketAddress());
+
+            // Start a new thread to continuously read messages from the server
+            new Thread(() -> {
+                try {
+                    String serverResponse;
+                    while ((serverResponse = reader.readLine()) != null) {
+                        System.out.println(serverResponse); // Display server messages
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }).start();
+
+            // Read user input and send it to the server
+            String userInputLine;
+            while ((userInputLine = userInput.readLine()) != null) {
+                writer.println(userInputLine); // Send user input to server
+                // Break the loop if the user types "/exit"
+                if (userInputLine.trim().equalsIgnoreCase("/exit")) {
+                    break;
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

Client Connection/2.jpg

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+import java.io.*;
+import java.net.*;
+
+public class SingleClient {
+    private static final String SERVER_ADDRESS = "localhost"; // Change this to the server's IP address if it's not
+                                                              // localhost
+    private static final int SERVER_PORT = 1234;
+
+    public static void main(String[] args) {
+        try (Socket socket = new Socket(SERVER_ADDRESS, SERVER_PORT);
+                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
+                PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
+                BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in))) {
+
+            System.out.println("Connected to server: " + socket.getRemoteSocketAddress());
+
+            // Start a new thread to continuously read messages from the server
+            new Thread(() -> {
+                try {
+                    String serverResponse;
+                    while ((serverResponse = reader.readLine()) != null) {
+                        System.out.println(serverResponse); // Display server messages
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }).start();
+
+            // Read user input and send it to the server
+            String userInputLine;
+            while ((userInputLine = userInput.readLine()) != null) {
+                writer.println(userInputLine); // Send user input to server
+                // Break the loop if the user types "/exit"
+                if (userInputLine.trim().equalsIgnoreCase("/exit")) {
+                    break;
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

Client Connection/3.jpg

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+// Save this as Server/ClientThread.java
+import java.io.*;
+import java.net.*;
+
+public class ClientThread implements Runnable {
+    private Socket socket;
+    private Server server;
+    private String clientName;
+
+    public ClientThread(Server server, Socket socket) {
+        this.server = server;
+        this.socket = socket;
+    }
+
+    public String getClientName() {
+        return clientName;
+    }
+
+    public void setClientName(String clientName) {
+        this.clientName = clientName;
+    }
+
+    public Socket getSocket() {
+        return socket;
+    }
+
+    public void setSocket(Socket socket) {
+        this.socket = socket;
+    }
+
+    @Override
+    public void run() {
+        try {
+            DataInputStream in = new DataInputStream(socket.getInputStream());
+            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
+
+            out.writeUTF("HI FROM SERVER");
+            while (!socket.isClosed()) {
+                try {
+                    if (in.available() > 0) {
+                        String input = in.readUTF();
+                        for (ClientThread thatClient : server.getClients()) {
+                            DataOutputStream outputParticularClient = new DataOutputStream(thatClient.getSocket().getOutputStream());
+                            outputParticularClient.writeUTF(input + " GOT FROM SERVER");
+                        }
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

Client Connection/4.jpg

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+import java.io.*;
+import java.net.*;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class MultiClientServer {
+    private static final int PORT = 1234;
+    private static volatile boolean running = true;
+    private static ExecutorService threadPool = Executors.newFixedThreadPool(10);
+    private static ServerSocket serverSocket;
+
+    public static void main(String[] args) {
+        // Start a thread to listen for shutdown commands
+        new Thread(() -> {
+            BufferedReader consoleReader = new BufferedReader(new InputStreamReader(System.in));
+            try {
+                while (running) {
+                    String command = consoleReader.readLine();
+                    if (command.equalsIgnoreCase("shutdown")) {
+                        running = false;
+                        System.out.println("Server is shutting down...");
+                        if (serverSocket != null && !serverSocket.isClosed()) {
+                            serverSocket.close();
+                        }
+                        threadPool.shutdown();
+                    }
+                }
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }).start();
+
+        try {
+            serverSocket = new ServerSocket(PORT);
+            System.out.println("Server is listening on port " + PORT);
+
+            // Main loop to accept client connections
+            while (running) {
+                try {
+                    Socket clientSocket = serverSocket.accept();
+                    System.out.println("Client connected: " + clientSocket.getRemoteSocketAddress());
+
+                    // Handle client communication in a new thread
+                    threadPool.execute(new ClientHandler(clientSocket));
+                } catch (IOException e) {
+                    if (!running) {
+                        System.out.println("Server has been shut down.");
+                    } else {
+                        e.printStackTrace();
+                    }
+                }
+            }
+        } catch (IOException e) {
+            if (!running) {
+                System.out.println("Server has been shut down.");
+            } else {
+                e.printStackTrace();
+            }
+        } finally {
+            if (serverSocket != null && !serverSocket.isClosed()) {
+                try {
+                    serverSocket.close();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }
+            threadPool.shutdown();
+        }
+    }
+
+    private static class ClientHandler implements Runnable {
+        private Socket clientSocket;
+
+        public ClientHandler(Socket clientSocket) {
+            this.clientSocket = clientSocket;
+        }
+
+        @Override
+        public void run() {
+            try (BufferedReader reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+                    PrintWriter writer = new PrintWriter(clientSocket.getOutputStream(), true)) {
+
+                String inputLine;
+                while ((inputLine = reader.readLine()) != null) {
+                    System.out.println("Received from client: " + inputLine);
+
+                    if (inputLine.trim().equalsIgnoreCase("/exit")) {
+                        writer.println("Server: Closing connection...");
+                        break;
+                    }
+
+                    writer.println("Server: " + inputLine);
+                }
+
+                System.out.println("Connection closed");
+            } catch (IOException e) {
+                e.printStackTrace();
+            } finally {
+                try {
+                    if (clientSocket != null && !clientSocket.isClosed()) {
+                        clientSocket.close();
+                    }
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }
+        }
+    }
+}

Client Connection/5.jpg

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+import java.io.*;
+import java.net.*;
+
+public class SingleClientServer {
+    private static final int PORT = 1234;
+
+    public static void main(String[] args) {
+        try (ServerSocket serverSocket = new ServerSocket(PORT)) {
+            System.out.println("Server is listening on port " + PORT);
+
+            // Wait for a client to connect
+            Socket clientSocket = serverSocket.accept();
+            System.out.println("Client connected: " + clientSocket.getRemoteSocketAddress());
+
+            // Set up input and output streams
+            BufferedReader reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
+            PrintWriter writer = new PrintWriter(clientSocket.getOutputStream(), true);
+
+            String inputLine;
+            while ((inputLine = reader.readLine()) != null) {
+                // Process input from client
+                System.out.println("Received from client: " + inputLine);
+
+                // Check if the received message is the exit command
+                if (inputLine.trim().equalsIgnoreCase("/exit")) {
+                    writer.println("Server: Closing connection..."); // Send a confirmation message to the client
+                    break; // Exit the loop to close the connection with the client
+                }
+
+                // Echo back to client
+                writer.println("Server: " + inputLine);
+            }
+
+            // Close streams and socket
+            reader.close();
+            writer.close();
+            clientSocket.close();
+            System.out.println("Connection closed");
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}