java使用UDP协议传输数据

http://blog.csdn.net/awj3584/article/details/24714515

UDP协议（User Datagram Protocol,用户数据报协议）不同于TCP协议，它是不可能靠的，但是它比TCP协议具有更快的传输速度，UDP发送的数据单元称为数据报，当网络传输UDP传输UDP数据报是无法保证数据能够到达目的地，也无法保证按发送的顺序到达目的地，也就是说先发送了“hello”,再发送了“world”,但接收方可能会先收到“world”,再收到“hello”,也有可能收不到数据，为什么呢？因为它是不可能靠的，在传输途中可能丢失了。但UDP比TCP跟适合与传输实时音频。下面是一个简单的UPD传输数据报的例子

服务器端：

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

 public class EchoServer {

     private DatagramSocket datagramSocket;

     private final int port = 8088;

     public static void main(String[] args) throws SocketException {
         new EchoServer().service();
     }

     public EchoServer() throws SocketException{
         datagramSocket = new DatagramSocket(port);
         System.out.println("服务器启动");
     }

     public String echo(String msg){
         return "echo:"+msg;
     }

     public void service(){
         while (true) {
             try {
                 DatagramPacket packet = new DatagramPacket(new byte[512], 512);
                 datagramSocket.receive(packet);
                 String msg = new String(packet.getData(), 0, packet.getLength());
                 System.out.println(packet.getAddress()+"/"+packet.getPort()+" msg:"+msg);
                 packet.setData(echo(msg).getBytes());
                 datagramSocket.send(packet);
             } catch (IOException e) {
                 e.printStackTrace();
             }

         }
     }

 }

客户端：

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.net.DatagramPacket;
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.net.SocketException;

 public class EchoClient {

     private String remoteHost="localhost";
     private int remotePort=8088;
     private DatagramSocket datagramSocket;

     public EchoClient() throws SocketException{
         datagramSocket = new DatagramSocket();
     }

     public static void main(String[] args) throws SocketException {
         new EchoClient().talk();
     }

     public void talk(){
         try {
             BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
             String msg = null;
             InetAddress address = InetAddress.getByName(remoteHost);
             while ((msg=reader.readLine())!=null) {
                 //发送数据报
                 byte [] buffer = msg.getBytes();
                 DatagramPacket packet = new DatagramPacket(buffer,buffer.length, address, remotePort);
                 datagramSocket.send(packet);
                 //接收数据报
                 DatagramPacket inputPacket = new DatagramPacket(new byte[512], 512);
                 datagramSocket.receive(inputPacket);
                 System.out.println(new String(inputPacket.getData(), 0 , inputPacket.getLength()));
                 if("bye".equals(msg)){
                     break;
                 }
             }

         } catch (IOException e) {
             e.printStackTrace();
         }finally{
             datagramSocket.close();
         }
     }

 }