udp协议 DatagramSocket

UDP协议是用户数据包协议，它面向非连接的协议，不与对方建立连接，而是直接把数据包发送出去；TCP协议是传输控制协议，它是可靠的，面向连接的，基于字节流的运输层通信协议。UDP因为没有连接过程，所以它的通信效果好，但正如此它的可靠性没有TCP协议高。如QQ就是UDP发送消息，有时会收不到消息。

package ZHANG.Socket.DatagramSocket;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

public class UpdSend {

/**
* @param args
*/
public static void main(String[] args) {
DatagramSocket ds;
DatagramPacket dp;
String strInfo = "hello wangs";
try {
ds = new DatagramSocket();
dp = new DatagramPacket("hello wang".getBytes(),"hello wang".length(),InetAddress.getByName("192.168.200.112"),3333);
ds.send(dp);
ds.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}

package ZHANG.Socket.DatagramSocket;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UpdRecev {

/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
DatagramSocket ds = new DatagramSocket(3333);
byte[] buf = new byte[1024];
DatagramPacket dp = new DatagramPacket(buf,1024);
ds.receive(dp);
String receInfo = new String(dp.getData(),0,dp.getLength());
System.out.println(receInfo+"from "+dp.getAddress().getHostAddress()+" port:"+dp.getPort());
ds.close();

}
}