5.0.3.Socket

Socket（网络套接字）是网络编程提供的一种机制，
通信的两端都要有socket，网络通信就是socket通信
数据在socket之间的io流通信

UDP通信
1.UDP服务器端创建

public class UdpServer {

    public static void main(String[] args){
        //create udp server
        //must assign port first ,greater than 8000
        DatagramSocket ds = null;
        try {       
             ds = new DatagramSocket(12000);        
            //define receive byte array
            //receive byte length
            byte[] bs = new byte[1024];
            DatagramPacket dp = new DatagramPacket(bs, bs.length);          
            //data package receive
            ds.receive(dp);
            
            InetAddress ia = dp.getAddress();
            //get data
            byte[] bs1 = dp.getData();
            String data = new String(bs1,0, bs1.length);            
            System.out.println(ia.getHostAddress()+" get "+ data);
            
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(ds !=  null){
                ds.close();
            }   
        }
    }
}

2.客户端创建

public class UdpClient {
    public static void main(String[] args){
        DatagramSocket ds =null;
        try {
            ds = new DatagramSocket();
            //define
            byte[] bs = "Hello".getBytes();
            //create receiver port
            InetAddress ia = InetAddress.getByName("192.168.1.6");
            DatagramPacket dp = new DatagramPacket(bs,bs.length,ia, 12000);
            //send
            ds.send(dp);
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(ds != null){
                ds.close();
            }
        }
    }
}