ChatServer.java

package clientserver;

import java.io.*;

import java.net.*;

import java.util.ArrayList;

public class ChatServer {

     

      static ArrayList<String> userNames = new ArrayList<String>();

      static ArrayList<PrintWriter> printWriters = new ArrayList<PrintWriter>();

     

      public static void main(String[] args) throws Exception{

            // TODO Auto-generated method stub

           System.out.println("Waiting for clients..."); 

           ServerSocket ss = new ServerSocket(9806);

           while (true)

           {

             Socket soc = ss.accept();

               System.out.println("Connection established");

             ConversationHandler handler = new ConversationHandler(soc);

             handler.start();
            //ss.close();
           
           }

            

      }
     
}

class ConversationHandler extends Thread

{

    Socket socket;

    BufferedReader in;

    PrintWriter out;

    String name;

    PrintWriter pw;

    static FileWriter fw;

    static BufferedWriter bw;

  

   public ConversationHandler(Socket socket) throws IOException {

        this.socket = socket;
        
      fw = new  FileWriter("C:\\Users\\Abhishek\\Desktop\\ChatServer-Logs.txt",true);

              bw = new BufferedWriter(fw);

              pw = new PrintWriter(bw,true);
        

      

    }

   public void run()

   {

        try

        {

            in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            out = new PrintWriter(socket.getOutputStream(), true);

           

            int count = 0;

            while (true)

            {

               if(count > 0)

               {

                    out.println("NAMEALREADYEXISTS");
                  // socket.close();

               }

               else

               {

                    out.println("NAMEREQUIRED");
                  //  socket.close();

               }

            

               name = in.readLine();

            

               if (name == null)

               {

                   return;

               }

        

               if (!ChatServer.userNames.contains(name))

               {

                  ChatServer.userNames.add(name);

                  break;

               }

             count++;

           }

           

            out.println("NAMEACCEPTED"+name);

            ChatServer.printWriters.add(out);

           

            while (true)

            {

                String message = in.readLine();

               

                if (message == null)

                {

                    return;

                }

               

                pw.println(name + ": " + message);

                for (PrintWriter writer : ChatServer.printWriters) {

                    writer.println(name + ": " + message);
                    writer.flush();

                }

            }

           

        }

        catch (Exception e)

        {

            System.out.println(e);

        }

   }

}