/**** EchoServer.java ****/

/**********************************************************************
*  Copyright (c) 1991 - 1997 Jerry Smith.
*
*  This software is provided for demonstration purposes only.  As
*  freely-distributed, modifiable source code, this software carries
*  absolutely no warranty.  Jerry Smith disclaims all warranties for
*  this software, including any implied warranties of merchantability
*  and fitness, and shall not be liable for damages of any type
*  resulting from its use.
*  Permission to use, copy, modify, and distribute this source code
*  for any purpose and without fee is hereby granted, provided that
*  the above copyright and this permission notice appear in all
*  copies and supporting documentation, and provided that Jerry Smith
*  not be named in advertising or publicity pertaining to the
*  redistribution of this software without specific, written prior
*  permission.
**********************************************************************/

import java.io.*;
import java.net.*;

public class EchoServer extends Thread {
  static final String APP_NAME = "EchoServer";
  static final int PORT = 2001;
  static ServerSocket serverSocket;
  static int port = PORT;
  Socket clientSocket;
  BufferedReader is = null;
  BufferedWriter os = null;

  public EchoServer(Socket cs) {
    clientSocket = cs;
  }

  public static void main(String args[]) {
    if (usageOnly(args))
      System.exit(0);
    initialize(args);
    while (true) {
      try {
        Socket clientSocket = serverSocket.accept();
        EchoServer es = new EchoServer(clientSocket);
        es.start();
      }
      catch (IOException e) {
        printMsg("Cannot accept client connection.");
      }
    }
  }

  public void run() {
    processClientRequest();
  }

  private static boolean usageOnly(String args[]) {
    if (args.length > 1 || (args.length == 1 &&
        (args[0].equalsIgnoreCase("-usage") ||
        args[0].equalsIgnoreCase("-help") ||
        args[0].equalsIgnoreCase("-h")))) {
      System.out.println("Usage:  java " + APP_NAME + " [<port>]");
      System.out.println("  The default port is 2001.");
      return true;
    }
    else
      return false;
  }

  private static void initialize(String args[]) {
    processCommandLine(args);
    try {
      serverSocket = new ServerSocket(port);
    }
    catch (IOException e) {
      printMsg("Cannot create server socket " +
        "on port:  " + port + ".  Exiting...");
      System.exit(0);
    }
  }

  private void processClientRequest() {
    try {
      os = new BufferedWriter(
        new OutputStreamWriter(clientSocket.getOutputStream()));
      is = new BufferedReader(
        new InputStreamReader(clientSocket.getInputStream()));
    }
    catch (IOException e) {
      printMsg("Cannot handle client connection.");
      cleanup();
      return;
    }
    try {
      String input = is.readLine();
      if (input != null) {
        input = APP_NAME + ": " + input;
        os.write(input, 0, input.length());
        os.flush();
      }
    }
    catch (IOException e) {
      printMsg("I/O error while processing client's print file.");
    }
    cleanup();
  }

  private void cleanup() {
    try {
      if (is != null)
        is.close();
      if (os != null)
        os.close();
      if (clientSocket != null)
        clientSocket.close();
    }
    catch (IOException e) {
      printMsg("I/O error while closing connections.");
    }
  }

  private static void processCommandLine(String args[]) {
    if (args.length != 1)
      return;
    port = Integer.parseInt(args[0]);
    if (port < 1 || port > 65535) {
      port = PORT;
      printMsg("Using port " + port + " instead.");
    }
  }

  private static void printMsg(String msg) {
    System.out.println(APP_NAME + ":  " + msg);
  }
}