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Commit f976e4ef authored by snapp's avatar snapp
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Add AllenTcpExample1Telnet1.java to homework1 folder

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package MV3500Cohort2021JulySeptember.homework1;;
import java.io.*;
import java.net.*;
import java.io.*;
import java.net.*;
import java.io.*;
import java.net.*;
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.
*
* Modifying his program is the basis for Assignment 1.
*
* 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
* @author brutzman
*/
public class AllenTcpExample1Telnet1
{
/**
* Program invocation, execution starts here
* @param args command-line arguments
*/
public static void main(String[] args)
{
try
{
System.out.println("TcpExample1Telnet has started and is waiting for a connection.");
System.out.println(" help: https://savage.nps.edu/Savage/developers.html#telnet");
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);
// Use Java io classes to write text (as opposed to
// unknown bytes of some sort) to the client
// The Socket object represents the connection between
// the server and client, including a full duplex connection
try (Socket clientConnection = serverSocket.accept()) // wait here for a client to connect
{
// OK we got something, time to respond!
// 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 John Allen "); // to remote client
ps.println("MOVES 2021 Cohort is well described by Johnny Smiles.");
System.out.println("This server response was written by John Allen " ); // to server console
// "flush()" in important in that it forces a write
// across what is in fact a slow connection
ps.flush();
}
System.out.println(" completed successfully.");
}
catch(IOException e)
{
System.err.println(" Pardon the interruption, networking issue"); // describe what is happening
System.err.println(e);
// Provide more helpful information to user if exception occurs due to running twice at one time
// brute force exception checking, can be brittle if exception message changes
// if (e.getMessage().equals("Address already in use: NET_Bind"))
if (e instanceof java.net.BindException)
System.err.println("*** Be sure to stop any other running instances of programs using this port!");
}
}
}
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