// This file contains material supporting section 3.7 of the textbook: // "Object Oriented Software Engineering" and is issued under the open-source // license found at www.lloseng.com import java.io.*; import ocsf.server.*; /** * This class overrides some of the methods in the abstract * superclass in order to give more functionality to the server. * * @author Dr Timothy C. Lethbridge * @author Dr Robert Laganière * @author François Bélanger * @author Paul Holden * @version July 2000 */ public class EchoServer extends AbstractServer { //Class variables ************************************************* /** * The default port to listen on. */ final public static int DEFAULT_PORT = 5555; //Constructors **************************************************** /** * Constructs an instance of the echo server. * * @param port The port number to connect on. */ public EchoServer(int port) { super(port); } //Instance methods ************************************************ /** * This method handles any messages received from the client. * * @param msg The message received from the client. * @param client The connection from which the message originated. */ public void handleMessageFromClient (Object msg, ConnectionToClient client) { System.out.println("Message received: " + msg + " from " + client); this.sendToAllClients(msg); } /** * This method overrides the one in the superclass. Called * when the server starts listening for connections. */ protected void serverStarted() { System.out.println ("Server listening for connections on port " + getPort()); } /** * This method overrides the one in the superclass. Called * when the server stops listening for connections. */ protected void serverStopped() { System.out.println ("Server has stopped listening for connections."); } //Class methods *************************************************** /** * This method is responsible for the creation of * the server instance (there is no UI in this phase). * * @param args[0] The port number to listen on. Defaults to 5555 * if no argument is entered. */ public static void main(String[] args) { int port = 0; //Port to listen on try { port = Integer.parseInt(args[0]); //Get port from command line } catch(Throwable t) { port = DEFAULT_PORT; //Set port to 5555 } EchoServer sv = new EchoServer(port); try { sv.listen(); //Start listening for connections } catch (Exception ex) { System.out.println("ERROR - Could not listen for clients!"); } } } //End of EchoServer class 

1. Currently the server ignores situations where clients connect or disconnect. Modify the server so that it prints out a nice message whenever a client connects or disconnects. (write code in EchoServer that overrides certain methods found in AbstractServer). 1. Currently the server ignores situations where clients connect or disconnect. Modify the server so that it prints out a nice message whenever a client connects or disconnects. (write code in EchoServer that overrides certain methods found in AbstractServer)