import java.net.*;
import java.io.*;
/**
 Plain SOCKS unaware UDP echo server and client.
*/
public class UDPEcho implements Runnable{
  
   private int port;
   private InetAddress hostIP;
   private DatagramSocket sock;

   private static final int BUF_SIZE = 1024;


   public UDPEcho(String host,int port) 
	  throws IOException,UnknownHostException{
      this.hostIP = InetAddress.getByName(host);
      this.port = port;
      sock = new DatagramSocket();
      System.out.println("UDP: "+sock.getLocalAddress()+":"+
                                 sock.getLocalPort());
      //sock.connect(hostIP,port);
   }

   public void send(String s) throws IOException{
      System.out.println("Sending:"+s);
      DatagramPacket packet = new DatagramPacket(s.getBytes(),
                                                 s.length(),
						 hostIP,
						 port);
      sock.send(packet);
   }

   public void run(){
      byte[] buf = new byte[BUF_SIZE];
      DatagramPacket incomingData = new DatagramPacket(buf,buf.length);
      try{
	  while(true){
	     sock.receive(incomingData);
	     System.out.println("UDP From:"+
			      incomingData.getAddress().getHostAddress()+":"+
			      incomingData.getPort());
	     System.out.println(new String(incomingData.getData(),
                                0,incomingData.getLength()));
             System.out.flush();
	     incomingData.setLength(buf.length);
	  }
      }catch(IOException io_ex){
	 io_ex.printStackTrace();
      }
   }

   public static void usage(){
      System.err.print(
      "Usage: java UDPEcho host port\n"+
      "OR\n"+
      "Usage: java UDPEcho port\n");
   }

   public static void doEcho(int port)throws IOException{
      byte[] buf = new byte[BUF_SIZE];
      DatagramPacket packet = new DatagramPacket(buf,buf.length);
      DatagramSocket sock = new DatagramSocket(port);
      
      System.out.println("Starting UDP echo on"+
                          sock.getLocalAddress().getHostAddress()+
                          ":"+sock.getLocalPort());
      while(true){
	 try{
	   sock.receive(packet);
	   sock.send(packet);
           System.out.print(
           "UDP From: "+packet.getAddress().getHostAddress()+":"+
                        packet.getPort()+
	   "\n"+
	   new String(packet.getData(),0,packet.getLength())+
	   "\n"
	   );
           System.out.flush();
           
	   packet.setLength(buf.length);
           //packet = new DatagramPacket(buf,buf.length);
	 }catch(IOException io_ex){
	 }
      }
   }

   public static void main(String args[]){
      int port;
      String host;

      if(args.length == 1){
	 try{
	   port = Integer.parseInt(args[0]);

	   doEcho(port);

	 }catch(IOException io_ex){
	   io_ex.printStackTrace();
	   System.exit(1);

	 }catch(NumberFormatException num_ex){
	   num_ex.printStackTrace();
	   System.exit(1);
	 }
      }else if(args.length == 2){
	 try{
	     host = args[0];
	     port = Integer.parseInt(args[1]);

	     UDPEcho ut = new UDPEcho(host,port);
	     Thread thread = new Thread(ut);
	     thread.start();

	     BufferedReader in = new BufferedReader(
				 new InputStreamReader(System.in));
             String s;
             System.out.print("Enter datagram:");
             s = in.readLine();
	     while(s != null){
		ut.send(s);
		try{
		   Thread.currentThread().sleep(100);
		}catch(InterruptedException i_ex){
		}
                System.out.print("Enter datagram:");
                s = in.readLine();
	     }
	     System.exit(1);

	 }catch(IOException io_ex){
	   io_ex.printStackTrace();
	   System.exit(1);
	 }catch(NumberFormatException num_ex){
	   num_ex.printStackTrace();
	   System.exit(1);
	 }

      }else{
	usage();
      }
   }

}//End of class