Schutt HW 1

assignments/src/MV3500Cohort2019JulySeptember/homework1/SchuttTcpExample1Telnet.java

+package MV3500Cohort2019JulySeptember.homework1;
+
+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, brutzman
+ */
+public class SchuttTcpExample1Telnet 
+{
+    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);
+            
+            // 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 Thomas' Client."); // to remote clientnc
+            System.out.println("This server response was written by Thomas' Server."); // 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 TcpExample1Telnet 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!");
+        }
+    }
+}