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

public class UDPServerDemo {
    static final int port = 4200;
    private byte[] buf = new byte[1000];
    private DatagramPacket dgp = new DatagramPacket(buf, buf.length);
    private DatagramSocket sk;

    public UDPServerDemo() {
	try {
	    sk = new DatagramSocket(port);
	    System.out.println("Server start....");
	    while (true) {
		sk.receive(dgp);
		String strReceived = "(" + dgp.getAddress() + ":"
			+ dgp.getPort() + ")"
			+ new String(dgp.getData(), 0, dgp.getLength());
		System.out.println(strReceived);
		String strOutMess = "";
		BufferedReader stdin = new BufferedReader(
			new InputStreamReader(System.in));
		strOutMess = stdin.readLine();
		String strOutput = "[Server say]:" + strOutMess;
		byte[] buf = strOutput.getBytes();
		DatagramPacket out = new DatagramPacket(buf, buf.length, dgp
			.getAddress(), dgp.getPort());
		sk.send(out);

	    }
	} catch (SocketException e) {
	    System.out.println("打開套接字錯(cuò)誤!");
	    System.exit(1);
	} catch (IOException e) {
	    System.out.println("數(shù)據(jù)傳輸錯(cuò)誤!");
	    e.printStackTrace();
	    System.exit(1);
	}
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
	// TODO Auto-generated method stub
	new UDPServerDemo();
    }

}