Java实现UDP组播(multicast)和单播(unicast)简单例子——局域网内

1.组播
a.接收端：

public class MulticastReceive {
    public static void main(String[] args) throws Exception {
        listener();
    }

    public static void listener() throws Exception{
        //组播地址
        InetAddress group = InetAddress.getByName("224.0.0.1");
        int port = 8888;
        //创建组播套接字
        MulticastSocket msr = null;
        try {
            msr = new MulticastSocket(port);
            //加入连接
            msr.joinGroup(group);
            byte[] buffer = new byte[8192];
            System.out.println("接收数据包启动！(启动时间: "+new Date()+")");
            while(true){
                //建立一个指定缓冲区大小的数据包
                DatagramPacket dp = new DatagramPacket(buffer, buffer.length);
                msr.receive(dp);
                String s = new String(dp.getData(),0,dp.getLength());
                //解码组播数据包
                System.out.println(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(msr!=null){
                try {
                    msr.leaveGroup(group);
                    msr.close();
                } catch (Exception e2) {
                }
            }
        }
    }
}

b.发送端

public class MulticastSender {
    public static void server() throws Exception{
        InetAddress group = InetAddress.getByName("224.0.0.1");//组播地址
        int port = 8888;
        MulticastSocket mss = null;
        try {
            mss = new MulticastSocket(port);
            mss.joinGroup(group);
            System.out.println("发送数据包启动！（启动时间"+new Date()+")");

            while(true){
                String message = "Hello "+new Date();
                byte[] buffer = message.getBytes();
                DatagramPacket dp = new DatagramPacket(buffer, buffer.length,group,port);
                mss.send(dp);
                System.out.println("发送数据包给 "+group+":"+port);
                TimeUnit.SECONDS.sleep(1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            try {
                if(mss!=null){
                    mss.leaveGroup(group);
                    mss.close();
                }
            } catch (Exception e2) {
            }
        }
    }

    public static void main(String[] args) throws Exception {
        server();
    }
}

2.单播
a.接收端：

public class UnicastReceive {

    // 演示udp通信接收端代码
    public static void main(String[] args) throws Exception {

        // 创建DatagramSocket对象(开放一个端口号)
        DatagramSocket datagramSocket = new DatagramSocket(8888) ;

        // 创建DatagramPacket对象(封装要接收的数据)
        byte[] bytes = new byte[1024];
        int len = bytes.length;
        while (true) {
            DatagramPacket datagramPacket = new DatagramPacket(bytes, len);

            // 调用DatagramSocket方法完成数据的接收
            System.out.println("接收数据开始................");
            datagramSocket.receive(datagramPacket);                 // 这个方法是一个阻塞方法,如果没有发送端发送数据过来，线程一直处于阻塞状态
            System.out.println("数据已接收................");

            // 获取发送端的ip地址
            InetAddress inetAddress = datagramPacket.getAddress();
            String ip = inetAddress.getHostAddress();

            // 解析数据
            byte[] data = datagramPacket.getData();         // 获取数据
            int length = datagramPacket.getLength();        // 获取数据的真实长度
            System.out.println(ip + "接收数据：" + new String(data, 0, length, "UTF-8"));

        }
        // 释放资源
//        datagramSocket.close();

    }

}

b.发送端：

public class UnicastSender {

    // 演示udp通信发送端代码
    public static void main(String[] args) throws Exception {

        // 创建DatagramSocket对(无参构造方法)
        DatagramSocket datagramSocket = new DatagramSocket() ;

        // 创建DatagramPacket对象(封装要发送的数据，以及接收端的ip地址和端口号)
        String s = "Hello,lalalala" ;
        byte[] bytes = s.getBytes("UTF-8");
        int len = bytes.length ;
        InetAddress inetAddress = InetAddress.getByName("172.16.10.160");
        int port = 32465 ;
        DatagramPacket datagramPacket = new DatagramPacket(bytes , len , inetAddress , port) ;

        // 调用DatagramSocket方法完成数据的发送
        datagramSocket.send(datagramPacket);

        // 释放资源
        datagramSocket.close();

    }

}

目前组播测试都ok，附带一个组播接收数据转换json格式代码片段：