Java中实现UDP协议的两个类,分别是DatagramPacket数据包类以及DatagramSocket套接字类。
UDP的套接字DatagramSocket相比于Socket、ServerSocket来说,是一个非常简单的概念,没有连接的含义。套接字只需要知道侦听和发送数据包的本地端口即可。
也就是在TCP协议中庸Socket类和ServerSocket类进行功能划分,UDP协议中只用一个数据包套接字DatagramSocket发送和接受数据即可。
发送和接收数据、地址和端口都封装在数据包类DatagramPacket中。
public DatagramPacket(byte[] buf,int length);
/*offset为buf缓冲区的偏移量*/
public DatagramPacket(byte[] buf,int offset,int length);
/*address表示目的地址 port表示目的端口*/
public DatagramPacket(byte[] buf,int offset,int length,InetAdress address, int port)
/*返回接受数据包的主机IP地址,通常用于获取接受到数据包的发送主机IP*/
public InetAdress getAdress();
/*返回数据包的主机端口号*/
public int getPort();
/*返回被接收或发送的缓冲区数据*/
public byte[] getData();
/*设置返回发出数据包的主机IP地址*/
public void setAdress(InetAdress iaddr);
/*设置要将此数据包发往远程主机上的端口号*/
public void setPort(int iport);
对于数据包套接字DatagramSocket来说,它只是发送或接收数据包的端口,不需要考虑链接。因此在客户端和服务器端都需要建立一个DatagramSocket对象,然后通过receive()方法接受数据包,通过send()方法发送数据包。
客户端发送1-26数字给服务器端;
服务器端返回对应的A-Z给客户端。
package web;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Scanner;
public class UDPCilent {
public static void main(String[] args) {
try {
/*UDP Cilent SEND*/
DatagramSocket socket=new DatagramSocket();
System.out.println("UDP Cilent Start...");
System.out.println("Enter 1 to 26 ,Server Will Return U A to Z:");
String info=new Scanner(System.in).next();
socket.send(new DatagramPacket(info.getBytes(), info.length(),InetAddress.getByName("127.0.0.1"),3000));
System.out.println("UDP Cilent Send Message...");
byte[] rec=new byte[1024];
DatagramPacket recivepacket=new DatagramPacket(rec, rec.length);
socket.receive(recivepacket);
System.out.println("Receive");
String reciveData=new String(recivepacket.getData(),0,recivepacket.getLength());
System.out.println("Receive from"+recivepacket.getAddress().getHostAddress()+":"+reciveData);
socket.close();
System.out.println("UDP Cilent close...");
} catch (Exception e) {
// TODO: handle exception
}
}
}
package web;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.Socket;
public class UDPServer {
public static void main(String[] args) {
try {
/*UDP Receive Message*/
DatagramSocket socket=new DatagramSocket(3000);
byte []bf=new byte[1024];
DatagramPacket packet=new DatagramPacket(bf, 1024);
System.out.println("UDP Server Start... Wait to Receive Message...");
socket.receive(packet);
String info=new String(packet.getData(),0,packet.getLength())+"from"+packet.getAddress().getHostAddress()+":"+packet.getPort();
System.out.println(info);
/*feedback*/
InetAddress address= packet.getAddress();
int port=packet.getPort();
String str=new String(packet.getData(),0,packet.getLength());
int renum=Integer.parseInt(str);
int feedback='A';
for(int i=1;i<=26;i++)
{
if(renum==i){
feedback=feedback+(i-1);
}
}
char back=(char) feedback;
String fbString=back+"";
byte[] fstr=fbString.getBytes();
DatagramPacket feed= new DatagramPacket(fstr,fstr.length,address,port);
socket.send(feed);
socket.close();
System.out.println("UDP Server close...");
} catch (Exception e) {
// TODO: handle exception
}
}
}