UDP通信

简单通信

类似于发短信

public class TestUDPClientDemo {
    public static void main(String[] args) throws Exception {
        //1.建立一个Socket
        DatagramSocket socket = new DatagramSocket();

        //2.建一个包
        String msg = "hi,laoge";

        //发送给谁
        InetAddress localhost = InetAddress.getByName("localhost");
        int port = 9090;

        //数据：数据的长度起始，要发给谁
        DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.getBytes().length,localhost,port);

        //3.发送包
        socket.send(packet);

        //4.关闭包
        socket.close();
    }

发送端

//还是要等待客户端的连接
public class TestUDPServerDemo {
    public static void main(String[] args) throws Exception{
        //开放端口
        DatagramSocket socket = new DatagramSocket(9090);
        //接收数据包
        byte[] buffer = new byte[1024];
        DatagramPacket packet = new DatagramPacket(buffer,0,buffer.length);

        socket.receive(packet);//阻塞接收

        System.out.println(packet.getAddress().getHostAddress());
        System.out.println(new String(packet.getData(),0,packet.getLength()));
    //关闭连接
        socket.close();
    }
}

接收端

并没有所谓的客户端和服务器之分

UDP聊天实现

public class TalkReceive implements Runnable{

    DatagramSocket socket = null;
    private int Port;
    private String msgfrom;

    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){
            try {
                //准备接收包裹
                byte[] buffer = new byte[1024];
                DatagramPacket datagramPacket = new DatagramPacket(buffer,0,buffer.length);
                socket.receive(datagramPacket);//阻塞式接收包裹
                byte[] data = datagramPacket.getData();
                String s = new String(data,0,data.length);
                System.out.println(msgfrom+":"+s);
                if (s.equals("bye")){
                    break;
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        socket.close();
    }
}

public class TalkSend implements Runnable{
    DatagramSocket socket = null;
    BufferedReader reader = null;

    private int Port;
    private String ToIp;
    private int Toport;

    public TalkSend(int Port, String toIp, int toport) {
        this.Port = Port;
        this.ToIp = toIp;
        this.Toport = toport;
        try {
            socket = new DatagramSocket(Port);
            reader = new BufferedReader(new InputStreamReader(System.in));
        } catch (SocketException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void run() {
        while(true){
            String data = null;
            try {

                data = reader.readLine();
                byte[] datas = data.getBytes();
                DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress(this.ToIp,this.Toport));
                socket.send(packet);

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

public class student {
    public static void main(String[] args) {
        new Thread(new TalkReceive(8888,"老师说")).start();
        new Thread(new TalkSend(7777,"localhost",9999)).start();
    }
}

public class Teacher {
    public static void main(String[] args) {
        new Thread(new TalkSend(5555,"localhost",8888)).start();
        new Thread(new TalkReceive(9999,"学生说")).start();
    }
}