Socket problem: read & write to same socket

I want to establish connection to a server(written by myself in Go language=
), read from socket, and then write into socket.

The connection can be established, and it reads correctly. But after that a=
nd when I want to write to socket, it closes the connection. I used wiresha=
rk to listen to the packets. I saw my program sent a FIN to the server side=
.. So the server receives nothing.

Note that the server side only sends one line into socket.

I later wrote a server in Java and a client in Go. They work fine in both r=
ead and write.

Thanks in advance!

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class DeserializerTester {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        Socket s = null;
        BufferedReader in = null;
        BufferedWriter out = null;
        //PrintWriter out = null;

        try {
            s = new Socket("127.0.0.1", 9999);
            in = new BufferedReader(new InputStreamReader(s.getInputStream()));
            //out = new PrintWriter(s.getOutputStream(), false);
            out = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
        } catch (UnknownHostException e) {
            System.err.println("Unknown host");
            System.exit(0);
        } catch (IOException e) {
            System.err.println("IO error");
            System.exit(1);
        }

        String msg = "";

        msg = in.readLine();
        System.out.println(msg);

        out.write("\"hi, socket\"");
        s.close();
    }

}