TcpExample1Telnet.java

package TcpExamples;

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

/**
 * The simplest possible TCP network program. It listens for
 * a connection, from telnet (telnet localhost 2317) or a program
 * you write, which we will do later. Right now the TcpExample simply
 * writes a string in response to a connection. 
 * 
 * Testing the running server program from telnet looks like this:
 * 
 * it154916:projects mcgredo$ telnet localhost 2317
 * Trying ::1...
 * Connected to localhost.
 * Escape character is '^]'.
 * This was written by the server
 * Connection closed by foreign host.
 * 
 * Notice that "This was written by the server" matches 
 * what is written by the code below, over the output stream.
 * 
 * After this first connection the program below drops out
 * the bottom of the program, and does not repeat itself.
 * The program exits.
 * 
 * @author mcgredo
 */
public class TcpExample1Telnet 
{

    @SuppressWarnings("ConvertToTryWithResources")
    public static void main(String[] args) 
    {
        try
        {
            System.out.println("TcpExample1Telnet has started and is waiting for a connection.");
            System.out.println("  enter (telnet localhost 2317) or (nc localhost 2317)..." );
			
            // The ServerSocket waits for a connection from a client.
            // It returns a Socket object when the connection occurs.
            ServerSocket serverSocket = new ServerSocket(2317);
            
            // The Socket object represents the connection between
            // the server and client, including a full duplex connection
            Socket clientConnection = serverSocket.accept();
            
            // Use Java io classes to write text (as opposed to
            // unknown bytes of some sort) to the client
            OutputStream os = clientConnection.getOutputStream();
            PrintStream ps = new PrintStream(os);
            
                    ps.println("This client response was written by server TcpExample1."); // to remote clientnc
            System.out.println("This server response was written by server TcpExample1."); // to server console
            
            // "flush()" in important in that it forces a write 
            // across what is in fact a slow connection
            ps.flush();
            
            clientConnection.close();
            System.out.println("TcpExample1 completed successfully.");
        }
        catch(IOException e)
        {
            System.out.println("problem with networking: " + e);
        }
    }
}