Institute of Inf. Tech. - Informatikai intézet

    import java.io.IOException;
    import java.io.ObjectInputStream;
    import java.io.ObjectOutputStream;
    import java.net.ServerSocket;
    import java.net.Socket;
 
    public class Server {
    	ServerSocket providerSocket;
    	Socket connection = null;
    	ObjectOutputStream out;
    	ObjectInputStream in;
    	String message;
 
    	Server() {
    	}
 
    	void run() {
    		try {
    			// 1. create a socket server listening to port 8080
    			providerSocket = new ServerSocket(8080, 10);
    			// 2. waiting for the connection (here we are waiting until next connection)
    			connection = providerSocket.accept();
    			// 3. create Input and Output streams
    			out = new ObjectOutputStream(connection.getOutputStream());
    			in = new ObjectInputStream(connection.getInputStream());
    			// 4. socket communication
    			do {
    				try {
    					message = (String) in.readObject();
    					System.out.println("client>" + message);
    					if (message.equals("bye")) {
    					    sendMessage("bye");
    					} 
    				} catch (ClassNotFoundException classnot) {
    					System.err.println("Data received in unknown format");
    				}
    			} while (!message.equals("bye"));
    		} catch (IOException ioException) {
    			ioException.printStackTrace();
    		} finally {
    			// 4: close connection
    			try {
    				in.close();
    				out.close();
    				providerSocket.close();
    			} catch (IOException ioException) {
    				ioException.printStackTrace();
    			}
    		}
    	}
 
    	void sendMessage(String msg) {
    		try {
    			out.writeObject(msg);
    			out.flush();
    			System.out.println("server>" + msg);
    		} catch (IOException ioException) {
    			ioException.printStackTrace();
    		}
    	}
 
    	public static void main(String args[]) {
    		Server server = new Server();
    		while (true) {
    			server.run();
    		}
    	}
    }

    import java.io.IOException;
    import java.io.ObjectInputStream;
    import java.io.ObjectOutputStream;
    import java.net.Socket;
    import java.net.UnknownHostException;
 
    public class Client {
    	Socket requestSocket;
    	ObjectOutputStream out;
    	ObjectInputStream in;
    	String message;
 
    	Client() {
    	}
 
    	void run() {
    		try {
    			// 1. try to connect to the socket: localhost:8080
    			requestSocket = new Socket("localhost", 8080);
    			// 2. Input and Output streams
    			out = new ObjectOutputStream(requestSocket.getOutputStream());
    			in = new ObjectInputStream(requestSocket.getInputStream());
    			// 3: communications
    			do {
    				try {
    					sendMessage("Hello server");
    					sendMessage("bye");
    					message = (String) in.readObject();
    				} catch (Exception e) {
    					System.err.println("data received in unknown format");
    				}
    			} while (!message.equals("bye"));
    		} catch (UnknownHostException unknownHost) {
    			System.err.println("You are trying to connect to an unknown host!");
    		} catch (IOException ioException) {
    			ioException.printStackTrace();
    		} finally {
    			// 4: close connection
    			try {
    				in.close();
    				out.close();
    				requestSocket.close();
    			} catch (IOException ioException) {
    				ioException.printStackTrace();
    			}
    		}
    	}
 
    	void sendMessage(String msg) {
    		try {
    			out.writeObject(msg);
    			out.flush();
    			System.out.println("client>" + msg);
    		} catch (IOException ioException) {
    			ioException.printStackTrace();
    		}
    	}
 
    	public static void main(String args[]) {
    		Client client = new Client();
    		client.run();
    	}
    }