java server clint

public class Client_Application {


    public static void main(String argv[]) throws Exception
 {
     while(true)
     {
        String sentence;
        String modifiedSentence;
        BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
        Socket clientSocket = new Socket("localhost", 6789);
        DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
        BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        sentence = inFromUser.readLine();
        outToServer.writeBytes(sentence + '\n');
        modifiedSentence = inFromServer.readLine();
        System.out.println("FROM SERVER: " + modifiedSentence);
        clientSocket.close();
     }
 }
}

public class Server_Application {
   public static void main(String argv[]) throws Exception
      {
          //System.out.println("This is Server Site");
          Scanner sc= new Scanner(System.in);
         String clientSentence;
         //String capitalizedSentence;
         ServerSocket welcomeSocket = new ServerSocket(6789);

         while(true)
         {
            Socket connectionSocket = welcomeSocket.accept();
            BufferedReader inFromClient =
               new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
            DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
            clientSentence = inFromClient.readLine();
            System.out.println("Received: " + clientSentence);
            clientSentence=sc.nextLine();
            //capitalizedSentence = clientSentence.toUpperCase() + '\n';
            outToClient.writeBytes(clientSentence+ '\n');
         }
      }
}