dgsclient.java

UDP服务器和客户端通信的简单例子

package inetaddressdemo;

import java.io.*;
import java.net.*;

class DGSClient
{
  public static void main (String [] args){
     String host = "localhost";
     // If user specifies a command-line argument, that argument
     // represents the host name.
     if (args.length == 1)
         host = args [0];
     DatagramSocket s = null;
     try{
        // Create a datagram socket bound to an arbitrary port.
        s = new DatagramSocket ();
        // Create a byte array that will hold the data portion of a
        // datagram packet's message. That message originates as a
        // String object, which gets converted to a sequence of
        // bytes when String's getBytes() method is called. The
        // conversion uses the platform's default character set.
        byte [] buffer;
        buffer = new String ("Send me a datagram").getBytes ();
        // Convert the name of the host to an InetAddress object.
        // That object contains the IP address of the host and is
        // used by DatagramPacket.
        InetAddress ia = InetAddress.getByName (host);
        // Create a DatagramPacket object that encapsulates a
        // reference to the byte array and destination address
        // information. The destination address consists of the
        // host's IP address (as stored in the InetAddress object)
        // and port number 10000 -- the port on which the server
        // program listens.
        DatagramPacket dgp = new DatagramPacket (buffer,
                                                  buffer.length,
                                                  ia,
                                                  10000);
        // Send the datagram packet over the socket.
        s.send (dgp);

        // Create a byte array to hold the response from the server.
        // program.
        byte [] buffer2 = new byte [100];
        // Create a DatagramPacket object that specifies a buffer
        // to hold the server program's response, the IP address of
        // the server program's computer, and port number 10000.
        dgp = new DatagramPacket (buffer2, buffer.length, ia, 10000);
        // Receive a datagram packet over the socket.
        s.receive (dgp);

        // Print the data returned from the server program and stored
        // in the datagram packet.
        System.out.println (new String (dgp.getData ()));
     }catch (IOException e){
         System.out.println (e.toString ());
     }
     finally{
        if (s != null)
           s.close ();
    }
   }
}