为什么我不能使用UDP在客户端和服务器之间发送数据包

我在Java中使用UDP协议在客户端和服务器之间进行通信时遇到问题 . 我制作了Client和Server类以及两个SingleCom负责发送和接收数据包的类 . 我试图测试连接（我在一台计算机和另一台服务器上运行客户端;两者都在同一端口上创建DatagramSocket）只需从客户端发送“START”字符串到服务器，然后该服务器应在控制台上打印字符串并发送返回“ACCEPTED”，但客户端和服务器都在其控制台上打印任何内容 . 有谁能告诉我发生了什么，为什么？下面我展示了简化的类（我在其他数据包中分离了服务器和客户端）：

//Client:
public class Client
{
    protected static InetAddress serverAddress;
    protected static InetAddress clientAdr;
    protected static int port;
    protected static SingleCom connection;
    public static final int PACKET_SIZE = 1024;

    public static void main(String[] args) throws IOException, InterruptedException
    {
        //get server address and port typed from console
        load();

        connection = new SingleCom();
        connection.initilize();
        Thread privcastTread = new Thread(connection);
        privcastTread.start();

        //sending the simplest packet
        connection.sendPacket("START", serverAddress);

    }

    public static synchronized void handlePacket(DatagramPacket packet, String msg) throws IOException
    {
        if (msg.startsWith("ACCEPTED"))
        {
            System.out.println("Accepted");
        }

    }

}

//SingleCom for Client
public class SingleCom implements Runnable
{
    DatagramSocket udpSocket;
    @Override
    public void run()
    {
        try
        {
            byte[] buffer = new byte[8192];
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

            while(true)
            {
                udpSocket.receive(packet);
                String msg = new String(buffer, 0, packet.getLength());
                Client.handlePacket(packet, msg);
                packet.setLength(buffer.length);
            }
        }
        catch (SocketException e)
        {
            System.exit(1);
        }
        catch (IOException e)
        {
            System.exit(1);
        }
    }

    public void initilize() throws IOException
    {
        udpSocket = new DatagramSocket(Client.port, InetAddress.getLocalHost());
    }

    public void sendPacket(String text, InetAddress target) throws IOException
    {
        byte[] sendedMsg = text.getBytes();
        DatagramPacket sendedPacket = new DatagramPacket(sendedMsg, sendedMsg.length, target, Client.port);
        udpSocket.send(sendedPacket);
    }

    public void sendPacket(String text) throws IOException
    {
        sendPacket(text, Client.serverAddress)
    }

    public void sendPacket(byte[] content) throws IOException
    {
        //byte[] sendedMsg = text.getBytes();
        DatagramPacket sendedPacket = new DatagramPacket(content, content.length, Client.serverAddress, Client.port);
        udpSocket.send(sendedPacket);
    }
}

//Server
public class Server
{
    protected static InetAddress serverAdr;
    protected static InetAddress clientAdr;
    protected static SingleCom connection;
    protected static int port;
    protected static int speed; //in KB/s

    private static FileOutputStream fos;

    public static void main(String[] args) throws IOException
    {
        load();

        connection = new SingleCom();
        connection.initilize();
        Thread privcastTread = new Thread(connection);
        privcastTread.start();
    }

    public static synchronized void handlePacket(DatagramPacket pakiet, String msg) throws IOException
    {
        String[] pieces;
        if (msg.startsWith("START"))
        {
            System.out.println(pieces[0]);
            connection.sendPacket("ACCEPTED", clientAdr);
        }
    }

}

//connection for Server
public class ServerCom implements Runnable
{
    DatagramSocket udpSocket;
    @Override
    public void run()
    {
        try
        {
            byte[] buffer = new byte[8192];
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

            while(true)
            {
                udpSocket.receive(packet);
                String msg = new String(buffer, 0, packet.getLength());
                Server.handlePacket(packet, msg);
                packet.setLength(buffer.length);
            }
        }
        catch (SocketException e)
        {
            System.exit(1);
        }
        catch (IOException e)
        {
            System.exit(1);
        }
    }

    public void initilize() throws IOException
    {
        udpSocket = new DatagramSocket(Server.port, InetAddress.getLocalHost());
    }

    public void sendPacket(String text, InetAddress target) throws IOException
    {
        byte[] sendedMsg = text.getBytes();
        DatagramPacket sendedPacket = new DatagramPacket(sendedMsg, sendedMsg.length, target, Server.port);
        udpSocket.send(sendedPacket);
    }

    public void sendPacket(String text) throws IOException
    {
        sendPacket(text, Server.clientAdr);
    }

}