java—UDP_public class udpclient { public static void main(s-优快云博客

本文链接：https://blog.youkuaiyun.com/beginnerdzz/article/details/119424817

本文详细介绍了使用UDP协议进行无连接通信的Java示例，包括单次发送、循环接收、多线程聊天服务，展示了如何创建DatagramSocket和DatagramPacket进行数据交换，并演示了如何实现简单的消息传递和断开连接机制。

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UDP

发短信：不用连接但是到知道地址

1.发送信息

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public class UDPclient {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket();

        String msg="你好 服务器";


        InetAddress inetAddress =InetAddress.getByName("localhost");
        int port=9090;
        DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, inetAddress, port);

        socket.send(packet);

        socket.close();
    }
}

public class UDPservre {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(9090);

        byte[] bytes = new byte[1024];

        DatagramPacket packet =new DatagramPacket(bytes,0,bytes.length);

        socket.receive(packet);

        System.out.println(new String(packet.getData(),0,packet.getLength()));



        socket.close();
    }
}

2.循环接受


public class UdpSeceiveDemo01   {
    public static void main(String[] args) throws Exception {
        DatagramSocket socket = new DatagramSocket(6666);
        while (true){
            //准备接受包裹的数组
            byte[] bytes = new byte[1024];

            //数据程序包
            DatagramPacket packet = new DatagramPacket(bytes,0,bytes.length);
            socket.receive(packet);//阻塞式接受包裹

            byte[] data = packet.getData();
            String receivedata = new String(data, 0, data.length);

            System.out.println(receivedata);

            //输出bye  断开连接
            if (new String(packet.getData(),0,packet.getLength()).equals("bye")){//单纯的s.equals("bye") s里面有1021个0 无法停止
                break;
            }
        }
        socket.close();
    }
}

3.多线程在线咨询

public class TalkReceive implements Runnable{
    private int port;
    private String msgFrom=null;
    private DatagramSocket socket=null;

    public TalkReceive(int port, String msgFrom) {
        this.port = port;
        this.msgFrom = msgFrom;
        try {
            socket = new DatagramSocket(port);
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }


    @Override
    public void run() {

        while (true){
            //准备接受包裹的数组
            byte[] bytes = new byte[1024];

            //数据程序包
            DatagramPacket packet = null;
            try {
                packet = new DatagramPacket(bytes,0,bytes.length);
                socket.receive(packet);//阻塞式接受包裹
            } catch (IOException e) {
                e.printStackTrace();
            }

            byte[] data = packet.getData();
            String receivedata = new String(data, 0, data.length);

            System.out.println(msgFrom+":"+receivedata);

            //输出bye  断开连接
            if (new String(packet.getData(),0,packet.getLength()).equals("bye")){//单纯的s.equals("bye") s里面有1021个0 无法停止
                break;
            }
        }
        socket.close();
    }

}

public class TalkSend implements Runnable {


    private int fromPort = 0;
    private String toIP=null;
    private int toPort=0;
    private DatagramSocket socket = null;
    private BufferedReader reader= null;

    public TalkSend(int fromPort, String toIP, int toPort) {
        this.fromPort = fromPort;
        this.toIP = toIP;
        this.toPort = toPort;
        try {
            socket = new DatagramSocket(fromPort);
        } catch (SocketException e) {
            e.printStackTrace();
        }
        reader = new BufferedReader(new InputStreamReader(System.in));
    }




    @Override
    public void run() {

        try {
            while (true) {

                String s = reader.readLine();
                DatagramPacket packet = new DatagramPacket(s.getBytes(), 0, s.getBytes().length, new InetSocketAddress(toIP, toPort));
                socket.send(packet);

                if (s.equals("bye")) {
                    break;
                }
            }
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}