Client.java

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class InWorke implements Runnable{

    BufferedReader odczyt=null;
    String slowo;
    ObjectInputStream ois=null;
    Message message;

    InWorke(ObjectInputStream ois) {
        this.ois=ois;
    }

    public void run() {
        while(true) {
            try {
                System.out.println("Client prepare to read");
                slowo = (String) ois.readObject();
                System.out.println("Client read: " + slowo);
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println(slowo);
            Thread.yield();
        }               }

}

class OutWorke implements Runnable{
    Socket socket=null;
    BufferedReader odczytWe=null;
    DataOutputStream zapis=null;
    String slowo=null;
    Message message; // it is the simple class to serialization
    ObjectOutputStream oos;

    OutWorke(Socket socket, ObjectOutputStream oos) {
        this.socket=socket;
        this.oos=oos;
    }

    public void run() {
        P.p("Start out worker client");
        while(true) {
            //odczytWe=new BufferedReader(new InputStreamReader(System.in));
            /*
            try {
                slowo=odczytWe.readLine();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            */
            slowo = "Hello, world";
            System.out.println("Client prepare to send");
            try {
                oos.writeObject(slowo);
                oos.flush();
                System.out.println("Client sent");
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            Thread.yield();
            break;
        }

    }
}

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

        Socket socket=null;
        ExecutorService exec= Executors.newCachedThreadPool();

        ObjectOutputStream oos=null;
        ObjectInputStream ois=null;

        try {
            socket=new Socket("localhost", 8881);
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            //wy=socket.getOutputStream();
            oos=new ObjectOutputStream(socket.getOutputStream());
            oos.flush();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            //we=socket.getInputStream();

            ois=new ObjectInputStream(socket.getInputStream());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        exec.execute(new OutWorke(socket, oos));
        exec.execute(new InWorke(ois));

    }
} 

Server.java

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class InWorker implements Runnable{

    Socket socket=null;
    //InputStream we=null;
    //OutputStream wy=null;
    String slowo=null;
    BufferedReader odczyt=null;
    ObjectOutputStream oos;
    ObjectInputStream ois;
    Message message=null;

    InWorker(Socket socket,ObjectInputStream ois) {
        this.socket=socket;
        this.ois=ois;
    }

    public void run() {
        while(true) {
            try {
                System.out.println("Server prepare to read");
                slowo=(String) ois.readObject();
                System.out.println("Server read: " + slowo);
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            System.out.println(slowo);
            Thread.yield();
        }

    }
}

class OutWorker implements Runnable{

    DataOutputStream zapis=null;
    BufferedReader odczyt=null;
    //OutputStream wy=null;
    String tekst=null;
    ObjectOutputStream oos=null;
    Message message;

    OutWorker(ObjectOutputStream oos) {
        this.oos=oos;
    }

    public void run() {
        while(true) {
            odczyt=new BufferedReader(new InputStreamReader(System.in));
            try {
                tekst=odczyt.readLine();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            try {
                oos.writeObject(tekst);
                oos.flush();
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            Thread.yield();
        }
    }

}

class P {
    public static void p(Object obj) {
        System.out.println(obj);
    }
}

public class Server {

    public static void main(String[] args) {
        ServerSocket serversocket=null;
        Socket socket=null;
        //InputStream we=null;
        //OutputStream wy=null;
        ObjectOutputStream oos=null;
        ObjectInputStream ois=null;

        ExecutorService exec= Executors.newCachedThreadPool();

        try {
            serversocket=new ServerSocket(8881);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            P.p("Server waits");
            socket=serversocket.accept();
            P.p("Server got");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            oos=new ObjectOutputStream(socket.getOutputStream());
            oos.flush();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {
            ois=new ObjectInputStream(socket.getInputStream());
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        exec.execute(new InWorker(socket, ois));
        exec.execute(new OutWorker(oos));

    }

}