Merge origin/master

assignments/src/MV3500Cohort2019JulySeptember/homework1/BrutzmanRefactorCopyTcpExample1Telnet.java → assignments/src/MV3500Cohort2019JulySeptember/homework1/BrutzmanRefactorTcpExample1Telnet.java

@@ -29,7 +29,7 @@ import java.net.*;
  * 
  * @author mcgredo, brutzman``  
  */
-public class BrutzmanRefactorCopyTcpExample1Telnet 
+public class BrutzmanRefactorTcpExample1Telnet 
 {
     public static void main(String[] args) 
     {
@@ -65,9 +65,15 @@ public class BrutzmanRefactorCopyTcpExample1Telnet
         catch(IOException e)
         {
             System.out.println("problem with networking: " + e);
-//          if (e.getClass() == java.net.BindException) // TODO whazzup?
-            if (e.getMessage().equals("Address already in use: NET_Bind"))
-                System.out.println("Be sure to stop any other running instances of this program.");
+
+            // Program modification: provide more helpful information to user if
+            // exception occurs when running twice at one time
+            
+            // brute force exception checking, can be brittle if exection message changes
+            // if (e.getMessage().equals("Address already in use: NET_Bind")) 
+
+            if (e instanceof java.net.BindException)
+                System.out.println("Be sure to stop any other running instances of this program!");
         }
     }
 }

examples/src/TcpExamples/TcpExample1Telnet.java

@@ -64,7 +64,10 @@ public class TcpExample1Telnet
         }
         catch(IOException e)
         {
-            System.out.println("problem with networking: " + e);
+            System.out.println("*** Problem with networking: " + 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!");
         }
     }
 }

examples/src/TcpExamples/TcpExample2ConnectionCounting.java

@@ -27,6 +27,7 @@ public class TcpExample2ConnectionCounting
         try
         {
             System.out.println("TcpExample2ConnectionCounting has started and is waiting for a connection.");
+            System.out.println("  help: https://savage.nps.edu/Savage/developers.html#telnet");
             System.out.println("  enter (nc localhost 2317) or (telnet localhost 2317)..." );
 			
             // ServerSocket waits for a connection from a client. 
@@ -84,6 +85,9 @@ public class TcpExample2ConnectionCounting
         catch(IOException e)
         {
             System.out.println("problem with networking: " + 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!");
         }
     }
 }

examples/src/TcpExamples/TcpExample3Client.java

@@ -41,13 +41,16 @@ public class TcpExample3Client {
 				String serverMessage = br.readLine();
 				System.out.println("==================================================");
 				System.out.println("Now we're talking!");
-				System.out.println("The message the server sent was " + serverMessage);
+				System.out.println("The message the server sent was '" + serverMessage + "'");
 				// socket gets closed, either automatically/silently this code (or possibly by server)
 			} // end while(true)
 		} 
 		catch (IOException e) {
 			System.out.println("Problem with client: "); // describe what is happening
 			System.out.println(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!");
 		}
 		// program exit: tell somebody about that
 		System.out.println("client exit");

examples/src/TcpExamples/TcpExample3Server.java

@@ -4,8 +4,8 @@ import java.io.*;
 import java.net.*;
 
 /**
- * Very slightly more complex than example1. A complete copy of example 2. The
- * only thing this does differently is introduce a loop into the response, so
+ * Very slightly more complex than example1, further modifying example 2.
+ * The only thing this does differently is introduce a loop into the response, so
  * you don't have to restart the program after one response. Also, it prints out
  * the socket pair the server sees. Run the program via telnet several times and
  * compare the socket pairs.
@@ -17,7 +17,7 @@ import java.net.*;
  *
  * telnet [ipNumberOfServerLaptop] 2317
  *
- * And have him display the socket pairs he got.
+ * And have the instructor display the socket pairs received.
  *
  * @author mcgredo
  */
@@ -31,7 +31,7 @@ public class TcpExample3Server {
 			// Notice that it is outside the loop; ServerSocket
 			// needs to be made only once.
 
-			System.out.println("TcpExample3Server has really started..."); // it helps debugging to put this on console first
+			System.out.println("TcpExample3Server has started..."); // it helps debugging to put this on console first
 			ServerSocket serverSocket = new ServerSocket(2317);
 
 			// Server is up and waiting (i.e. "blocked" or paused)
@@ -45,11 +45,10 @@ public class TcpExample3Server {
 				OutputStream os = clientConnection.getOutputStream();
 				PrintStream  ps = new PrintStream(os);
 
-				ps.println("This was written by the server"); // this goes back to client!
+				ps.println("This message was produced by the server."); // this gets sent back to client!
 
-				// Print some information locally about the Socket
-				// connection. This includes the port and IP numbers
-				// on both sides (the socket pair.)
+				// Print some information locally about the Socket connection. 
+                // This includes the port and IP numbers on both sides (the socket pair).
 				InetAddress localAddress = clientConnection.getLocalAddress();
 				InetAddress remoteAddress = clientConnection.getInetAddress();
 
@@ -60,8 +59,7 @@ public class TcpExample3Server {
 				// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54876 ))
 				// Socket pair: (( /0:0:0:0:0:0:0:1, 2317 ), ( /0:0:0:0:0:0:0:1, 54881 ))
 				//
-				// Why is the first IP/port the same, while the second set has
-				// different ports?
+				// Why is the first IP/port the same, while the second set has different ports?
 				System.out.println("TcpExample3Server socket pair: (( " + localAddress.toString() + ", " + localPort + " ), ( "
 						+ remoteAddress.toString() + ", " + remotePort + " ))");
 
@@ -73,8 +71,12 @@ public class TcpExample3Server {
 				clientConnection.close(); // like it or not, you're outta here!
 			}
 		} 
-		catch (IOException e) {
+		catch (IOException e)
+        {
 			System.out.println("problem with networking");
+            // 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!");
 		}
 	}
 }

examples/src/TcpExamples/TcpExample4HandlerThread.java

@@ -8,7 +8,7 @@ import java.net.*;
 /**
  * Handles all the logic associated with one connection
  * by running in a thread of its own. This is the server
- * portion as well, so we artifically invent what happens
+ * portion as well, so we artificially invent what happens
  * if the server can't respond to a connection for 10 sec.
  * 
  * @author Don McGregor
@@ -45,7 +45,7 @@ public class TcpExample4HandlerThread extends Thread
              OutputStream os = socket.getOutputStream();
               PrintStream ps = new PrintStream(os);
 
-			 final long TIMEOUT = 10000; // 10000 milliseconds = 10 seconds
+			 final long TIMEOUT = 2000; // 2000 milliseconds = 2 seconds, 10000 milliseconds = 10 seconds
 			 System.out.println("TcpExample4HandlerThread pausing for TIMEOUT=" + TIMEOUT + "ms"); // debug
              Thread.sleep(TIMEOUT); // 10 seconds