import java.io.*
import java.net.*
class ConnectDemo {
public static void main(String args[]) { 
   try {
     Socket s = new Socket("10.5.18.213",225);
     DataInputStream inp = new DataInputStream(s.getInputStream());
     boolean more_data = true;
     System.out.println("Established connection");
     while(more_data) {
        String line = inp.readLine();
        if(line == null) more_data = false;
        else System.out.println(line);
     }
   }
   catch(IOException e) {
 	System.out.println("IO error " + e)
   }
}





import java.io.*;
import java.net.*;
class SimpleServer {
	public static void main(String arg[]) {
		try {
			ServerSocket sock = new ServerSocket(7500);
			Socket newSock = sock.accept();
			DataInputStream inp = new DataInputStream(newsock.getInputStream());
			PrintStream outp = new PrintStream(newsock.getOutputStream());
			outp.println("Hello: enter QUIT to exit);
			boolean more_data = true;
			while (more_data) {
				String line = inp.readLine();
				if(line == null) more_data = false;
				else {
				   outp.println("From the server: " + line + "\n");
				   if(line.trim().equals("QUIT"))
					more_data = false;
				}
			}
		        newsock.close();
                  }
                  catch(Exception e) {
	               System.out.println("IO error " + e);
	 	  }
}




import java.io.*;
import java.net.*;
class ThreadHandler extends Thread {
	Socket newsock;
	int n;
	ThreadHandler(Socket s, int v) {
		newsock = s;
		n = v;
	}
	public void run() {
		try {
			DataInputStream inp = new DataInputStream(newsock.getInputStream());
			PrintStream outp = new PrintStream(newsock.getOutputStream());
			outp.println("Hello::enter QUIT to exit");
			boolean more_data = true;

			while (more_data) {
				String line = inp.readLine();
				if(line == null) more_data = false;
				else {
			   	outp.println("From the server: " + line + "\n");
			   	if(line.trim().equals("QUIT"))
				more_data = false;
				}
			}
	        	newsock.close();
		}
		catch (Exception e) {
			System.out.println("IO error " + e);
		}
          }
}


class ConcurrentServer {
	public static void main(String args[]) {
		int nreq = 1;
		try {
			ServerSocket sock = new ServerSocket(7500);
			for (;;) {
				Socket newsock = sock.accept();
				System.out.println("Creating thread ...");
				Thread t = new ThreadHandler(newsock, nreq);
				t.start();
				nreq++;
			}
		}
		catch(Exception e) {
			System.out.println("IO error " + e);
		}
	}
}




import java.io.*;
import java.net.*;
class DatagramDemo {
	public static int server_port = 7500;
	public static int client_port = 7501;
	public static DatagramSocket dgsock;
	public static byte buffer[] = new byte[512];

	public static void DgServer() throws Exception {
		System.out.println("Server starts ... ");
		int ptr = 0;
		for(;;) {
			int nextchar = System.in.read();
			switch(nextchar) {
				case -1: System.out.println("Exiting ..."); return;
				 
				case '\n': dgsock.send (new DatagramPacket(buffer, ptr, 					   inet.Address.getLocalHost(), client_port)); 
				           ptr = 0; break;
				
				default: buffer[ptr++] = (byte)nextchar;
			}
		}
	}

	
	public static void DgClient() throws Exception {
		System.out.println("Client starts ...");
		for (;;) {
			DatagramPacket pkt = new DatagramPacket(buffer, buffer.length);
			dgsock.receive(pkt);
			System.out.println(new String (pkt.getData(), 0, 0, pkt.getLength()));
		}
	}

	public static static void main(String args[]) throws Exception {
		if(args.length != 1) 
			System.out.println("Wrong number of arguments");
		else if (args[0].equals("client")) {
					dgsock = new DatagramSocket(client_port);
					DgClient();
		}
		else if (args[0].equals("server")) {
					dgsock = new DatagramSocket(server_port);
					DgServer();
		}
	}
}
}