import java.io.BufferedReader; 
import java.io.BufferedWriter; 
import java.io.FileReader; 
import java.io.FileWriter; 
import java.io.IOException; 
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 
import java.net.InetSocketAddress; 
import java.net.SocketException; 


public class Server { 
private static int number=0; 

public static void main(String[] args) throws IOException { 
// TODO Auto-generated method stub 
byte[] by = new byte[1024]; 
String s ; 
String s1; 
String s2; 
DatagramSocket ds = new DatagramSocket(9000); 
DatagramPacket dp = new DatagramPacket(by,by.length); 
DatagramPacket dp1 =null; 
FileWriter fw =new FileWriter("f:/ss/ss1.txt"); 
BufferedWriter bw = new BufferedWriter(fw); 
while(true){ 
ds.receive(dp); 
++number; 
s = new String(dp.getData(),0,dp.getLength()); 
s1 = s.substring(1); 
s2 = s.substring(0,1); 
Integer it = new Integer(s2); 
int i = it.intValue(); 
System.out.println(s1); 
s2 = s.substring(0,1); 
System.out.println(number); 
if(number==i){ 
bw.write(s1); 
bw.newLine(); 
bw.flush(); 
}else{ 
number--; 
} 
System.out.println(number); 
by = s2.getBytes(); 
dp1 = new DatagramPacket(by,by.length,new InetSocketAddress("127.0.0.1",8888)); 
ds.send(dp1); 
} 

} 

}