Update

assignments/src/MV3500Cohort2024JulySeptember/homework1/Romero/Homework.java

-package MV3500Cohort2024JulySeptember.homework1.Romero;
-
-public class Homework {
-
-    public static void main(String args[]) {
-        System.out.println("Hello world!");
-    }
-}
\ No newline at end of file

assignments/src/MV3500Cohort2024JulySeptember/homework1/Romero/ReneHW1.java

+package MV3500Cohort2024JulySeptember.homework1.Romero;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+/**
+ * <p>
+ * The simplest possible TCP network program, opening a socket and waiting for a reply. 
+ * It listens for any socket connection response, either from telnet (telnet localhost 2317)
+ * or another program that you write (which we will do later). 
+ * Once a socket connection is established, TcpExample1Telnet simply
+ * writes a string in response to that connection and finishes, exiting.
+ * 
+ * <p>
+ * As an alternative to running the Windows (or other operating system) console, 
+ * you can instead run the NetBeans terminal window.  If you are on Windows,
+ * NetBeans is looking for Cygwin installation (for Unix-like compatibility)
+ * with details at <a href="https://savage.nps.edu/Savage/developers.html#Cygwin" target="blank">Savage Developers Guide: Cygwin</a>.
+ * Modifying this program is the basis for Assignment 1.
+ * </p>
+ * 
+ * <p>
+ * Testing the running server program from telnet looks like this:
+ * </p>
+ * <pre>
+ * it154916:projects mcgredo$ <b>telnet localhost 2317</b>
+ * Trying ::1...
+ * Connected to localhost.
+ * Escape character is '^]'.
+ * This was written by the server
+ * Connection closed by foreign host.
+ * </pre>
+ * <p>
+ * Notice that "This was written by the server" matches 
+ * what is written by the code below, over the output stream.
+ * </p>
+ * 
+ * <p>
+ * After this first connection the program below drops to
+ * the bottom of the method, and does not repeat itself.
+ * In other words, the program exits.
+ * </p>
+ * 
+ * @see <a href="../../../src/TcpExamples/TcpExample1TerminalLog.txt" target="_blank">TcpExample1TerminalLog.txt</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample1NetBeansConsoleTelnet.png" target="_blank">TcpExample1NetBeansConsoleTelnet.png</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample1NetBeansConsoleTelnet.pdf" target="_blank">TcpExample1NetBeansConsoleTelnet.pdf</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample1ScreenshotNetcat.png" target="_blank">TcpExample1ScreenshotNetcat.png</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample1ScreenshotTelnet.png" target="_blank">TcpExample1ScreenshotTelnet.png</a>
+ * @see <a href="https://savage.nps.edu/Savage/developers.html#Cygwin" target="blank">Savage Developers Guide: Cygwin</a>
+ * @see <a href="https://savage.nps.edu/Savage/developers.html#telnet" target="blank">Savage Developers Guide: telnet</a>
+ * 
+ * @author mcgredo
+ * @author brutzman@nps.edu
+ */
+
+public class ReneHW1 
+{
+    /** Default constructor */
+    public ReneHW1()
+    {
+        // default constructor
+    }
+    /**
+     * Program invocation, execution starts here
+     * @param args command-line arguments
+     */
+    public static void main(String[] args)
+    {
+        try
+        {
+            System.out.println(ReneHW1.class.getName() + " has started and is waiting for a connection.");
+            System.out.println("  help:     https://savage.nps.edu/Savage/developers.html#telnet");
+            System.out.println("  terminal: enter (telnet localhost 2317) or, for macOS (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()) // listen, 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 server " + ReneHW1.class.getName()); // to remote client
+                System.out.println("This server response was written by server " + ReneHW1.class.getName()); // 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(ReneHW1.class.getName() + " completed successfully.");
+        }
+        catch(IOException ioe)
+        {
+            System.err.println("Exception with " + ReneHW1.class.getName() + " networking:"); // describe what is happening
+            System.err.println(ioe);
+            // 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 (ioe instanceof java.net.BindException)
+                System.err.println("*** Be sure to stop any other running instances of programs using this port!");
+        }
+    }
+}
\ No newline at end of file

assignments/src/MV3500Cohort2024JulySeptember/homework2/Romero/README.md

+# Rene Romero Homework 2
+
+***
+
+## Description
+
+

assignments/src/MV3500Cohort2024JulySeptember/homework2/Romero/RomeroServerHW2.java

+package MV3500Cohort2024JulySeptember.homework2.Romero;
+
+import java.io.IOException;
+import java.net.*;
+
+/**
+ * This server program works a bit differently by creating and dispatching a
+ * new thread to handle multiple incoming socket connections, one after another, all running in parallel.
+ * This advanced technique is often used in high=performance high=capacity server programs.
+ * 
+ * @see TcpExample4Client
+ * @see TcpExample4HandlerThread
+ *
+ * @see <a href="../../../src/TcpExamples/TcpExample4TerminalLog.txt" target="blank">TcpExample4TerminalLog.txt</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceDiagram.png" target="blank">TcpExample4SequenceDiagram.png</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceSketch.png" target="blank">TcpExample4SequenceSketch.png</a>
+ *
+ * @author Don McGregor
+ * @author Don Brutzman
+ * @author MV3500 class
+ */
+public class RomeroServerHW2
+{
+    /** Default constructor */
+    public RomeroServerHW2()
+    {
+        // default constructor
+    }
+    /**
+     * Program invocation, execution starts here
+     * @param args command-line arguments
+     */
+    public static void main(String[] args)
+    {
+        try {
+            ServerSocket             serverSocket = new ServerSocket(2317);
+            Socket                   clientConnectionSocket;
+            TcpExample4HandlerThread handlerThread;
+
+            int connectionCount = 0; // state variable
+
+            System.out.println(RomeroServerHW2.class.getName() + " ready to accept socket connections...");
+            while (true) // infinite loop
+            {
+                clientConnectionSocket = serverSocket.accept(); // block! until connected
+
+                connectionCount++; // unblocked, got another connection
+                
+                // TODO option for the student, provide initial message *to the client*
+                // that we are handing off to a dispatch thread... because that is polite behavior.
+                // Plenty of code in Example3, we instead let our proxy thread
+                // TcpExample4HandlerThread introduce itself to the client.
+                
+                System.out.println("=============================================================");
+                System.out.println(RomeroServerHW2.class.getName() + ".handlerThread created for connection #" + connectionCount + "...");
+                
+                // hand off this aready-created and connected socket to constructor
+                handlerThread = new TcpExample4HandlerThread(clientConnectionSocket); 
+                handlerThread.start();// invokes the run() method in that object
+                System.out.println(RomeroServerHW2.class.getName() + ".handlerThread is now dispatched and running, using most recent connection...");
+                
+                // while(true) continue looping, serverSocket is still waiting for another customer client
+            }
+        } 
+        catch (IOException e) {
+            System.out.println("Problem with " + RomeroServerHW2.class.getName() + " networking:"); // describe what is happening
+            System.out.println("Error: " + e);
+            // Provide more helpful information to user if exception occurs due to running twice at one time
+            if (e instanceof java.net.BindException) {
+                System.out.println("*** Be sure to stop any other running instances of programs using this port!");
+            }
+        }
+        System.out.println("============================================================="); // execution complete
+    }
+}

assignments/src/MV3500Cohort2024JulySeptember/homework2/Romero/TcpExample4Client.java

+package MV3500Cohort2024JulySeptember.homework2.Romero;
+
+import java.io.*;
+import java.net.*;
+//import java.time.LocalTime; // conversion?
+
+/**
+ * This client program establishes a socket connection to the {@link TcpExample4DispatchServer},
+ * then checks how long it takes to read the single line it expects as a server response.
+ * No fancy footwork here, it is pretty simple and similar to {@link TcpExample3Client}.
+ * 
+ * @see TcpExample4DispatchServer
+ * @see TcpExample4HandlerThread
+ *
+ * @see <a href="../../../src/TcpExamples/TcpExample4TerminalLog.txt" target="blank">TcpExample4TerminalLog.txt</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceDiagram.png" target="blank">TcpExample4SequenceDiagram.png</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceSketch.png" target="blank">TcpExample4SequenceSketch.png</a>
+ * 
+ * @author Don McGregor
+ * @author Don Brutzman
+ * @author MV3500 class
+ */
+public class TcpExample4Client
+{
+    /** Default constructor */
+    public TcpExample4Client()
+    {
+        // default constructor
+    }
+    static String DESTINATION_HOST = "localhost";
+    static int    MAX_LOOP_COUNT   = 4;
+
+    /**
+     * Program invocation, execution starts here
+     * @param args command-line arguments
+     */
+    public static void main(String[] args) {
+        try {
+            System.out.println(TcpExample4Client.class.getName() + " start, loop " + MAX_LOOP_COUNT + " times");
+            System.out.println("=======================================================");
+            for (int loopCount = 1; loopCount <= MAX_LOOP_COUNT; loopCount++) // loop then exit
+            {
+                System.out.println(TcpExample4Client.class.getName() + " creating new socket #" + loopCount + "...");
+
+                // We request an IP to connect to ("localhost") and
+                // port number at that IP (2317). This establishes
+                // a connection to that IP in the form of the Socket
+                // object; the server uses a ServerSocket to wait for
+                // connections.This particualar example is interacting
+                // with what it expects is a server that writes a single text
+                // line after 10 sec.
+                long startTime = System.currentTimeMillis();
+
+                // open a socket for each loop
+		Socket socket = new Socket(DESTINATION_HOST, 2317);
+
+                // Setup.  Read the single line written by the server.
+                // We'd do things a bit differently if many lines to be read
+                // from the server, instead of one only.
+                InputStream is = socket.getInputStream();
+                Reader isr = new InputStreamReader(is);
+                BufferedReader br = new BufferedReader(isr);
+
+                String serverMessage = br.readLine(); // blocks
+                long readTime = System.currentTimeMillis();
+                long timeLength = readTime - startTime;
+
+                System.out.println(TcpExample4Client.class.getName() + ": message received from server='" + serverMessage + "'");
+                System.out.println(TcpExample4Client.class.getName() + ": time msec required for read=" + timeLength);
+                System.out.println("=======================================================");
+                // To push this further, launch multiple copies of TcpExample4Client simultaneously
+            }
+            System.out.println(TcpExample4Client.class.getName() + " complete");
+            // main method now exits
+        } catch (IOException e) {
+            System.out.println("Problem with " + TcpExample4Client.class.getName() + " networking:networking:"); // describe what is happening
+            System.out.println("Error: " + e);
+            // Provide more helpful information to user if exception occurs due to running twice at one time
+            if (e instanceof java.net.BindException) {
+                System.out.println("*** Be sure to stop any other running instances of programs using this port!");
+            }
+        }
+    }
+}

assignments/src/MV3500Cohort2024JulySeptember/homework2/Romero/TcpExample4HandlerThread.java

+package MV3500Cohort2024JulySeptember.homework2.Romero;
+
+import java.io.*;
+import java.net.*;
+
+/**
+ * <p>
+ * This utility class supports the {@link TcpExample4DispatchServer} program,
+ * handling all programming logic needed for a new socket connection
+ * to run in a thread of its own. This is the server
+ * portion as well, so we artificially invent what happens
+ * if the server can't respond to a connection for several seconds.
+ * </p>
+ * <p>
+ * Warning: do not run this class!  It is created and used automatically by {@link TcpExample4DispatchServer} at run time.
+ * </p>
+ * 
+ * @see TcpExample4Client
+ * @see TcpExample4DispatchServer
+ *
+ * @see <a href="../../../src/TcpExamples/TcpExample4TerminalLog.txt" target="blank">TcpExample4TerminalLog.txt</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceDiagram.png" target="blank">TcpExample4SequenceDiagram.png</a>
+ * @see <a href="../../../src/TcpExamples/TcpExample4SequenceSketch.png" target="blank">TcpExample4SequenceSketch.png</a>
+ * 
+ * @author Don McGregor
+ * @author Don Brutzman
+ * @author MV3500 class
+ */
+public class TcpExample4HandlerThread extends Thread
+{
+    /** The socket connection to a client */
+    Socket socket;
+    
+    /** 
+     * The thread constructor creates the socket from a ServerSocket, waiting for the client to connect,
+     * and passes that socket when constructing the thread responsible for handling the connection.
+     * 
+     * @param socket The socket connection handled by this thread
+     */
+    TcpExample4HandlerThread(Socket socket)
+    {
+        this.socket = socket;
+    }
+    /**
+     * Program invocation and execution starts here - but is illegal and unwanted, so warn the unsuspecting user!
+     * @param args command-line arguments
+     */
+    public static void main(String[] args)
+    {
+        System.out.println ("*** TcpExample4HandlerThread is not a standalone executable progam.");
+        System.out.println ("*** Please run TcpExample4DispatchServer instead... now exiting.");
+    }
+    
+    /** Handles one connection. We add an artificial slowness
+     * to handling the connection with a sleep(). This means
+     * the client won't see a server connection response for ten seconds (default).
+     */
+    // @overriding run() method in Java Thread class is deliberate
+    @Override 
+    public void run()
+    {
+        try
+        {
+            System.out.println(TcpExample4HandlerThread.class.getName() + " starting to handle a thread...");
+            
+            // get the connection output stream, then wait a period of time. 
+            OutputStream os = socket.getOutputStream();
+            PrintStream ps = new PrintStream(os);
+
+            final long TIMEOUT = 2000; // 2000 milliseconds = 2 seconds, 10000 milliseconds = 10 seconds
+            System.out.println(TcpExample4HandlerThread.class.getName() + " pausing for TIMEOUT=" + TIMEOUT + "ms" + 
+                               " to emulate computation and avoid server-side overload"); 
+            Thread.sleep(TIMEOUT);
+                
+            // ps is the PrintStream is the Java way to use System.print() to pass data along the socket.
+            ps.println("This message was written by the server " + TcpExample4HandlerThread.class.getName()); // TODO insert socket count here!
+            ps.flush();     // make sure that it indeed escapes current process and reaches the client
+            socket.close(); // all clear, no longer need socket
+            System.out.println(TcpExample4HandlerThread.class.getName() + " finished handling a thread, now exit.");
+        }
+        catch(IOException | InterruptedException e) // either a networking or a threading problem
+        {
+            System.out.println("Problem with " + TcpExample4HandlerThread.class.getName() + " networking:"); // describe what is happening
+            System.out.println("Error: " + e);
+            
+            // Provide more helpful information to user if exception occurs due to running twice at one time
+            if (e instanceof java.net.BindException)
+                System.out.println("*** Be sure to stop any other running instances of programs using this port!");
+        }
+    }
+}