Socket编程---使用无连接的数据报(UDP) 进行通信（转）

使用无连接的数据报(UDP) 进行通信

什么是Datagram？
数据报是网上传输的独立数据包 ，数据报是否能正确地到达目的地，到达的时间，顺序，内容的正确性均没有保障。
 
java中使用Datagram与DatagramPacket类
DatagramSocket类利用UDP协议来实现客户与服务器的Socket.
send():发送数据报
receive(): 接收数据报

 

 以下为流程

 

 

 

 

以下为简单示例，不含一些异常处理、判空处理。

 

一、服务器端

package com.network;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPServer
{

    public static void main(String[] args)throws Exception
    {
        DatagramSocket datagramSocket = new DatagramSocket(5678);

        byte[] buffer = new byte[100];

        DatagramPacket packet = new DatagramPacket(buffer,100);

        datagramSocket.receive(packet);

        byte[] data = packet.getData();

        int i = packet.getLength();

        String content = new String(data,0,i);

        System.out.println("content from client : " + content);

        int length = content.length();

        String strLength = String.valueOf(length);

        byte[] b = strLength.getBytes();

        InetAddress address = packet.getAddress();

        int port = packet.getPort();

        DatagramPacket packet2 = new DatagramPacket(b,b.length,address,port);

        System.out.println("length: " + new String(b,0,b.length));

        datagramSocket.send(packet2);

        datagramSocket.close();


    }

}

 

 

 

二、客户端

 

package com.network;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

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

        String content = "hello world!";

        byte[] buffer = content.getBytes();

        InetAddress address = InetAddress.getByName("localhost");

        DatagramPacket packet = new DatagramPacket(buffer,buffer.length,address,5678);

        datagramSocket.send(packet);

        byte[] b = new byte[100];

        DatagramPacket packet2 = new DatagramPacket(b,100);

        datagramSocket.receive(packet2);

        byte[] b2 = packet2.getData();

        int l = packet2.getLength();

        String str = new String(b2,0,l);

        System.out.println("length of string : " + str);

        datagramSocket.close();
    }
}