package TcpExamples;

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

/**
 * Very slightly more complex than example1. A complete copy of example 2. The
 * only thing this does differently is introduce a loop into the response, so
 * you don't have to restart the program after one response. Also, it prints out
 * the socket pair the server sees. Run the program via telnet several times and
 * compare the socket pairs.
 *
 * telnet localhost 2317
 *
 * If you're sophisticated you can contact the instructor's computer while
 * running this program.
 *
 * telnet [ipNumberOfServerLaptop] 2317
 *
 * And have him display the socket pairs he got.
 *
 * @author mcgredo
 */
public class TcpExample3Server {

	@SuppressWarnings("ConvertToTryWithResources")
	public static void main(String[] args)
	{
		try {
			// ServerSocket waits for a connection from a client. 
			// Notice that it is outside the loop; ServerSocket
			// needs to be made only once.

			System.out.println("TcpExample3Server has really started..."); // it helps debugging to put this on console first
			ServerSocket serverSocket = new ServerSocket(2317);

			// Server is up and waiting (i.e. "blocked" or paused)
			// Loop, infinitely, waiting for client connections.
			// Stop the program somewhere else.
			while (true)
			{
				Socket clientConnection = serverSocket.accept(); // block until connected to a client
				
				// Now hook everything up (i.e. set up the streams), Java style:
				OutputStream os = clientConnection.getOutputStream();
				PrintStream  ps = new PrintStream(os);

				ps.println("This was written by the server"); // this goes back to client!

				// Print some information locally about the Socket
				// connection. This includes the port and IP numbers
				// on both sides (the socket pair.)
				InetAddress localAddress = clientConnection.getLocalAddress();
				InetAddress remoteAddress = clientConnection.getInetAddress();

				int  localPort = clientConnection.getLocalPort();
				int remotePort = clientConnection.getPort();

				// My socket pair connection looks like this, to localhost:
				// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54876 ))
				// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 ))
				//
				// Why is the first IP/port the same, while the second set has
				// different ports?
				System.out.println("TcpExample3Server socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( "
						+ remoteAddress.toString() + ", " + remotePort + " ))");

				// Notice the use of flush() and close(). Without
				// the close() to Socket object may stay open for 
				// a while after the client has stopped needing this
				// connection. Close() explicitly ends the connection.
				ps.flush();
				clientConnection.close(); // like it or not, you're outta here!
			}
		} 
		catch (IOException e) {
			System.out.println("problem with networking");
		}
	}
}