Homework 1

07/16
by
Bernd

assignments/src/MV3500Cohort2020JulySeptember/homework1/WeissenbergerTcpExample1Telnet.java

+
+package MV3500Cohort2020JulySeptember.homework1;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+/**
+ * Simple TCP Telnet Server, MV3500 Homework 1
+ * copied parts from: TcpExample1Telnet.java by @author mcgredo & @author brutzman
+ * @date 07/16/2020
+ * @author Loki
+ */
+public class WeissenbergerTcpExample1Telnet {
+        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()) {
+                // 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 Loki's server TcpExample1."); // to remote clientnc
+                ps.println(" _       _    _"+"\r\n"+"| |     | |  (_)"+"\r\n"+"| | ___ | | ___"+"\r\n"+"| |/ _ \\| |/ / |"+"\r\n"+"| | (_) |   <| |"+"\r\n"+"|_|\\___/|_|\\_\\_|");
+                System.out.println("This server response was written by server TcpExample1."); // to server console
+                System.out.println(" _       _    _"+"\n"+"| |     | |  (_)"+"\n"+"| | ___ | | ___"+"\n"+"| |/ _ \\| |/ / |"+"\n"+"| | (_) |   <| |"+"\n"+"|_|\\___/|_|\\_\\_|");
+
+                // "flush()" in important in that it forces a write
+                // across what is in fact a slow connection
+                ps.flush();
+            }
+            System.out.println("TcpExample1 completed successfully.");
+        }
+        catch(IOException e)
+        {
+            System.err.println("Problem with TcpExample1Telnet networking:"); // describe what is happening
+            System.err.println("Error: " + 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!");
+        }
+    }
+}