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 blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

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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();}}