Client

package clientelisa;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ClientElisa {

    Socket socket;
    boolean stop = true;

    ClientElisa() {
        try {
            socket = new Socket("127.0.0.1", 33061);
            DataOutputStream tmpOut = new DataOutputStream(socket.getOutputStream());
            tmpOut.writeUTF("10 + 10");
            tmpOut.flush();
        } catch (IOException ex) {
            Logger.getLogger(ClientElisa.class.getName()).log(Level.SEVERE, null, ex);
        }

        try {
            ServerSocket ss = new ServerSocket(1000);
            while (stop) {
                try {
                    socket = ss.accept();
//            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
//            out.println("ciao");
                    DataInputStream in = new DataInputStream(socket.getInputStream());

                    String str = in.readUTF().toString();

                    if (!str.equals("")) {
                        System.out.println(str);


                        stop = false;
                    }

                    socket.close();

                } catch (IOException ex) {
                    Logger.getLogger(ClientElisa.class.getName()).log(Level.SEVERE, null, ex);
                }
            }


        } catch (IOException ex) {
            Logger.getLogger(ClientElisa.class.getName()).log(Level.SEVERE, null, ex);
        }

    }

    public static void main(String[] args) {
        ClientElisa ce = new ClientElisa();
    }

}