*** ECHO CLIENT ***

import java.net.*;


import java.io.*;





public class echoClient {





  public static void main(String[] args) {





    Socket theSocket;


    String hostname;


    DataInputStream theInputStream;


    DataInputStream userInput;


    PrintStream theOutputStream;


    String theLine;





    if (args.length > 0) {


      hostname = args[0];


    }


    else {


      hostname = "LOCALHOST";


    }





    try {


      theSocket = new Socket(hostname, 9999);


      theInputStream = new DataInputStream(theSocket.getInputStream());


      theOutputStream = new PrintStream(theSocket.getOutputStream());


      userInput = new DataInputStream(System.in);


      while (true) {


        theLine = userInput.readLine();


        //System.out.println("?"+theLine);

        if (theLine.equals(".")) break;


        theOutputStream.println(theLine);


        //System.out.println(theInputStream.readLine());


      }


    }  // end try


    catch (UnknownHostException e) {


      System.err.println(e);


    }


    catch (IOException e) {


      System.err.println(e);


    }





  }  // end main





}  // end echoClient






	*** ECHO 3 ***

import java.io.*;

import java.net.*;




                      class echoThread extends Thread
                        {

                        String line;
                        DataInputStream is;
                        PrintStream os;
                        Socket clientSocket;

                        public echoThread(Socket cl)
                          {
                            clientSocket = cl;
                          }
                        public void run()
                          {
                            try
                            {
                              is = new DataInputStream(clientSocket.getInputStream());
                              os = new PrintStream(clientSocket.getOutputStream());
                              while(true)
                                {
                                  line = is.readLine();
                                  os.println(line);
                                }
                            }
                                catch(IOException e)
                                  {
                                    System.out.println(e);
                                  }
                          }


                        }



                      public class echo3 {


                           public static void main(String args[]) {



                       // declaration section:

                       // declare a server socket and a client socket for the server

                       // declare an input and an output stream



                               ServerSocket echoServer = null;

                               String line;

                               DataInputStream is;

                               PrintStream os;

                               Socket clientSocket = null;



                       // Try to open a server socket on port 9999

                       // Note that we can't choose a port less than 1023 if we are not

                       // privileged users (root)



                             //  try {

                             //     echoServer = new ServerSocket(9999);

                             //  }

                             //  catch (IOException e) {

                             //     System.out.println(e);

                             //  }



       // Create a socket object from the ServerSocket to listen and accept

                       // connections.

                       // Open input and output streams



                        //try {

                        //          clientSocket = echoServer.accept();

                         //         is = new DataInputStream(clientSocket.getInputStream());

                         //         os = new PrintStream(clientSocket.getOutputStream());



                       // As long as we receive data, echo that data back

                       // to the client.



                                  while (true) {

                                    line = is.readLine();

                                    os.println(line);

                                    System.out.println(line);

                                  }

                           //    }

                    //    catch (IOException e) {

                             //     System.out.println(e);

                            //   }

                           }

                       }






	*** ECHO 4 ***

import java.io.*;

import java.net.*;




                      class echoThread extends Thread
                        {

                        String line;
                        DataInputStream is;
                        PrintStream os;
                        Socket clientSocket;

                        public echoThread(Socket cl)
                          {
                            clientSocket = cl;
                          }
                        public void run()
                          {
                            try
                            {
                              is = new DataInputStream(clientSocket.getInputStream());
                              os = new PrintStream(clientSocket.getOutputStream());
                              while(true)
                                {
                                  line = is.readLine();
                                  os.println(line);
                                  System.out.println(line);
                                }
                            }
                                catch(IOException e)
                                  {
                                    System.out.println(e);
                                  }
                          }


                        }

                      public class echo4
                        {
                          public static void main(String args[])
                            {
                              Socket clientSocket;
                              ServerSocket echoServer = null;

                              try {
                                    echoServer = new ServerSocket(9999);
                                  }
                                catch (IOException e)
                                  {}
                              try {
                                    while(true)
                                    {
                                      clientSocket = echoServer.accept();
                                      echoThread et = new echoThread(clientSocket);
                                      et.start();
                                    }
                                  }
                                catch (Exception e)
                                  {}
                              }
                          }






	*** CHAT ***

import java.io.*;

import java.net.*;

import java.util.*;




                      class echoThread extends Thread
                        {

                        String line;
                        DataInputStream is;
                        PrintStream os;
                        Socket clientSocket;

                        public echoThread(Socket cl)
                          {
                            clientSocket = cl;
                          }
                        public void run()
                          {
                            try
                            {
                              is = new DataInputStream(clientSocket.getInputStream());
                              os = new PrintStream(clientSocket.getOutputStream());
                              while(true)
                                {
                                  line = is.readLine();
                                  os.println(line);
                                  System.out.print(clientSocket.getInetAddress().getHostName() +">");
                                  System.out.println(line);
                                }
                            }
                                catch(IOException e)
                                  {
                                    System.out.println(e);
                                  }
                          }


                        }

                      public class Chat
                        {
                          public static void main(String args[])
                            {

                              Vector clientName = new Vector();
                              Socket clientSocket;
                              ServerSocket echoServer = null;

                              try {
                                    echoServer = new ServerSocket(9999);
                                  }
                                catch (IOException e)
                                  {}
                              try {
                                    while(true)
                                    {
                                      clientSocket = echoServer.accept();
                                      echoThread et = new echoThread(clientSocket);
                                      et.start();
                                      clientName.addElement(clientSocket.getInetAddress().getHostName());
                                    }
                                  }
                                catch (Exception e)
                                  {}
                              }
                          }