LoeffelmanAssignment1Tcp2.java

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package MV3500Cohort2018JulySeptember.homework1;

import java.io.OutputStream;
import java.io.PrintStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;

/**
 *
 * @author garrettloeffelman
 */
public class LoeffelmanAssignment1Tcp2 {

    /**
     * @param args command-line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        try
        {
            // ServerSocket waits for a connection from a client. 
            // Notice that it is outside the loop; ServerSocket
            // needs to be made only once.
			
            int connectionCount = 0; // state
            int portNumber = 2317;
            
            ServerSocket serverSocket = new ServerSocket(portNumber); // server decides here what port to listen on.
			// of interest: often client doesn't care what port it uses locally when connecting to that server port.

            // Loop, infinitely, waiting for client connections.
            // Stop the program somewhere else.
            while(true)
            {
                Socket clientConnection = serverSocket.accept(); // blocks! then proceeds once a connection is "accept"ed
				
				connectionCount++; // got another one!
				
                OutputStream os = clientConnection.getOutputStream();
                PrintStream ps = new PrintStream(os);
                if(connectionCount < 2){
				ps.println("Nice job! You (the client) connected to port " + portNumber + ", lets see if it stays open!"); // to remote client
				ps.println("type 'nc -z -v {host-name-here} 2315-2320'");
                                System.out.println("A client connected to this server and was instructed to check open ports"); // to server console
                }
                if(connectionCount > 2){
                    ps.println("WOW loeffelmanExample2 Port 2317 is still open, Don't worry, when we close the server it will close");
                }
                            System.out.println("This is the server response by LoeffelmanExample2");
                            
                                ps.println("You were connection #" + connectionCount + ", by my count");
                

                // 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();       // remember the prior question, why are 2 ports different?
                
                // 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 )) note IPv6
                // 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("Socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( " + 
                                    remoteAddress.toString() + ", " + remotePort + " ))");
                
                System.out.println("got another connection, #" + connectionCount); // report progress
				
                // 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();
            }
       }
        catch(Exception e)
        {
            System.out.println("problem with networking: " + e);
        }
    }
    
}