这个问题在这里已经有答案了：

如何检测udp数据包丢失(（5个答案）
上个月关门了。
为了获得可靠的连接，您必须使用tcp。
但是，我想知道是否有一种方法可以修改我的代码，这样我就可以在udp中检查丢失的数据包

try {
        DatagramSocket socket = new DatagramSocket(5000);

        while(true) {
            byte[] buffer = new byte[50];
            DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
            socket.receive(packet);
            System.out.println("Text received is: " + new String(buffer, 0, packet.getLength()));

            String returnString = "echo: " + new String(buffer, 0, packet.getLength());
            byte[] buffer2 = returnString.getBytes();
            InetAddress address = packet.getAddress();
            int port = packet.getPort();
            packet = new DatagramPacket(buffer2, buffer2.length, address, port);
            socket.send(packet);
        }

    } catch(SocketException e) {
        System.out.println("SocketException: " + e.getMessage());
    } catch(IOException e) {
        System.out.println("IOException: " + e.getMessage());
    }
}