Client blocks!

I have this simple client/server application, but for some reason the
client blocks after typing the first input (of course the server is
running an the client is connected):

import java.io.*;
import java.net.*;

public class Server {

    public static void main(String[] args) {

        ServerSocket serverSocket = null;
        Socket ss = null;
        BufferedReader in = null;
        PrintWriter out = null;

        try {
             serverSocket = new ServerSocket(4444);

             System.out.println("CRAP1");
             ss = serverSocket.accept();
             System.out.println("CRAP2");
             in = new BufferedReader(new
InputStreamReader(ss.getInputStream()));
             out = new PrintWriter(ss.getOutputStream());

             String bob = null;

             while ((bob = in.readLine()) != null)
             {
                 System.out.println("CRAP3");
                 out.println(bob + "from server");
                 System.out.println(bob);
             }
             serverSocket.close();
         }

        catch (IOException e) {
            e.printStackTrace();
        }
    }

}

import java.io.*;
import java.net.*;

public class Client {

    public static void main(String[] args) {
        Socket socket = null;
        PrintWriter out = null;
        BufferedReader in = null;
        BufferedReader user = null;
        try
        {
            String fromServer, fromUser;

            // Connect to server.
            socket = new Socket("localhost",4444);

     // Out channel.
            out = new PrintWriter(socket.getOutputStream());

     // In channel.
            in = new BufferedReader(new
InputStreamReader(socket.getInputStream()));

            // Input from user.
     user = new BufferedReader(new InputStreamReader(System.in));

            while ((fromServer = in.readLine()) != null)
            {
                System.out.println(fromServer);
                fromUser = user.readLine();

                if (fromUser != null)
                {
                    out.println(fromUser);
                }
            }

        }catch(Exception e)
        {
            System.out.println(e.getMessage());
        }
    }

}