PHP将数据发送到Java守护进程

我在将数据从PHP脚本发送到Java守护程序时遇到一些问题。

这是Java:

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Listener implements Runnable {
    ServerSocket listenerSocket;
    Socket connection = null;
    ObjectOutputStream out;
    ObjectInputStream in;
    String message;
    @Override
    public void run()
    {
        try{
            listenerSocket = new ServerSocket(7331);
            System.out.println("Waiting for connection");
            connection = listenerSocket.accept();
            System.out.println("Connection received from " + connection.getInetAddress().getHostName());
            out = new ObjectOutputStream(connection.getOutputStream());
            out.flush();
            in = new ObjectInputStream(connection.getInputStream());
            do{
                try{
                    message = (String)in.readObject();
                    System.out.println("client>" + message);
                }
                catch(ClassNotFoundException classnot){
                    System.err.println("Data received in unknown format");
                }
            }while(!message.equals("bye"));
        }
        catch(IOException ioException){
            ioException.printStackTrace();
        }
        finally{
            try{
                in.close();
                out.close();
                listenerSocket.close();
            }
            catch(IOException ioException){
                ioException.printStackTrace();
            }
        }
    }
}

以下是PHP代码：

    <?php
    header('Content-Type: text/html; charset=utf-8');
    $fp = fsockopen("127.0.0.1", 7331, $errno, $errstr);
    if (!$fp) {
        echo "ERROR: $errno - $errstr<br />'n";
    } else {
        fwrite($fp, "yaydata");
        echo fread($fp, 26);
        fclose($fp);
    }
?>

这是我在Java:中遇到的错误

Waiting for connection
Connection received from localhost.localdomain
java.io.StreamCorruptedException: invalid stream header: 6675636B
        at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:804)
        at java.io.ObjectInputStream.<init>(ObjectInputStream.java:299)
        at com.cj.panel.Listener.run(Listener.java:25)
        at java.lang.Thread.run(Thread.java:744)
Exception in thread "Thread-0" java.lang.NullPointerException
        at com.cj.panel.Listener.run(Listener.java:41)
        at java.lang.Thread.run(Thread.java:744)

我似乎看不出这是怎么回事。我是这个跨平台网络的新手，所以任何帮助都很感激。