Java 服务器没有'；无法检测第二个客户端连接

我的问题是，当我打开第二个客户端时，服务器似乎没有检测到第二个客户端被打开。第一次打开客户机时，它工作正常，服务器检测到客户机已连接

服务器：

public class Server {

Socket previousSocket = null;

private static int port = 9001;

public static void main(String[] args) throws Exception {
    ServerSocket serverSocket = new ServerSocket(port);
    System.out.println("[SERVER] Server successfully launched on port: " + port);
    
    DatagramSocket UDPSocket = new DatagramSocket(9002);
    
    Socket previousSocket = null;
    while (true) {
        Socket newSocket = serverSocket.accept();

       System.out.println("new client connected");
        
        
        if (previousSocket == null) { 
            previousSocket = newSocket;
            
            System.out.println("1 st client");
            
            
        } else {
            System.out.println("2 nd client");
            previousSocket = null;
        }
       
       
        byte[] data = new byte[500];
        DatagramPacket received = new DatagramPacket(data, data.length);
        
        while(true) {
            UDPSocket.receive(received);
            
            String receivedData = new String(received.getData());
            
            System.out.println(receivedData);
        }
    }
}
}

客户：

public ChatClient() throws UnknownHostException, IOException {

    Socket socket = new Socket("127.0.0.1", 9001);

    Scanner scanner = new Scanner(System.in);
    
    DatagramSocket UDPSocket = new DatagramSocket();
    
    while(scanner.hasNextLine()) {
        String message = scanner.nextLine();
        InetAddress ip = InetAddress.getByName("127.0.0.1");
                
        DatagramPacket packet = new DatagramPacket(message.getBytes(), message.getBytes().length, ip, 9002);
        UDPSocket.send(packet);
    }
}

---

下面的循环永远不会结束，这就是问题的原因

        while(true) {
            UDPSocket.receive(received);
            
            String receivedData = new String(received.getData());
            
            System.out.println(receivedData);
        }

内部

while（true）

调用

UDPSocket.receive（received）从不退出，因此
serverSocket.accept（）只被调用一次。然而，当您显然只使用端口9002发送和接收数据时，为什么您首先在端口9001上有一个ServerSocket？