Datagram.java

import java.net.*;

class Datagram 
{
	public static int serverPort = 998;
	public static int clientPort = 999;
	public static int buffer_size = 1024;
	public static DatagramSocket ds;
	public static byte buffer[] = new byte[buffer_size];
	public static void TheServer() throws Exception 
	{
		int pos=0;
		while (true) 
		{
			int c = System.in.read();
			switch (c)
			{
				case -1:
				System.out.println("Server Quits.");
				return;
				case '\r':
				break;
				case '\n':
				ds.send(new DatagramPacket(buffer,pos,
				InetAddress.getLocalHost(),clientPort));
				pos=0;
				break;
				default:
				buffer[pos++] = (byte) c;
			}
		}
	}
	public static void TheClient() throws Exception 
	{
		while(true) 
		{
			DatagramPacket p = new DatagramPacket(buffer, buffer.length);
			ds.receive(p);
			System.out.println(new String(p.getData(), 0, p.getLength()));
		}
	}
	public static void main(String args[]) throws Exception 
	{
		if(args.length == 1) 
		{
			ds = new DatagramSocket(serverPort);
			TheServer();
		} 
		else
		{
			ds = new DatagramSocket(clientPort);
			TheClient();
		}
	}
}