updates to support compatible chat client using Java console and keyboard to...

updates to support compatible chat client using Java console and keyboard to provide messages, using MulticastUdpChatKeyboardSender

examples/src/UdpExamples/MulticastUdpReceiver.java

 package UdpExamples;
 
+import static UdpExamples.MulticastUdpChatKeyboardSender.LINE_TERMINATOR;
 import edu.nps.moves.dis7.utilities.DisThreadedNetworkInterface;
 import java.io.*;
 import java.net.*;
@@ -38,6 +39,8 @@ public class MulticastUdpReceiver
 
     private static final boolean INFINITE_READ_LOOP = true;
     private static NetworkInterface ni;
+    
+    public static final int BUFFER_LENGTH = 1500;
 
     /**
      * Program invocation, execution starts here
@@ -47,7 +50,7 @@ public class MulticastUdpReceiver
     {
         MulticastSocket multicastSocket = null;
         InetSocketAddress group = null;
-        ByteBuffer buffer = ByteBuffer.allocate(1500);
+        ByteBuffer buffer = ByteBuffer.allocate(BUFFER_LENGTH);
         DatagramPacket packet = new DatagramPacket(buffer.array(), buffer.capacity());
         
         try {
@@ -67,49 +70,75 @@ public class MulticastUdpReceiver
             group = new InetSocketAddress(multicastAddress, DESTINATION_PORT);
             
             // Join group useful on receiving side
-            multicastSocket.joinGroup(group, ni = DisThreadedNetworkInterface.findIpv4Interface());
+            multicastSocket.joinGroup(group, ni = DisThreadedNetworkInterface.findIpv4Interface()); // utility function
             // You can join multiple groups here
             
-            System.out.println("Multicast address/port: " + multicastAddress.getHostAddress() + "/" + DESTINATION_PORT);
+            System.out.println("Multicast address/port: " + multicastAddress.getHostAddress() + "/" + DESTINATION_PORT +
+                               " isBound=" + multicastSocket.isBound());
+                            // unnecessary, no server involved:  +  "isConnected=" + multicastSocket.isConnected()
             System.out.println("Multicast packets received log:");
 
-            int index, count = 0; // initialize
-            float firstFloat, secondFloat;
+            int              messageCount = 0; // initialize
             StringBuilder firstCharacters = new StringBuilder();
             char nextChar;
 
-            while (true) { // true is always true, so this is an infinite loop that continues until interrupted
-                multicastSocket.receive(packet);
-                count++;
+            while (true) // true is always true, so this is an infinite loop that continues until interrupted
+            {
+                // initializations for this loop
+                int      messageIndex = 0;    
+                float   firstFloat = 0.0f;
+                float  secondFloat = 0.0f;
+                
+                multicastSocket.receive(packet); // this method call will block until a packet is received
+                messageCount++;
 
-                nextChar = ' ';
+                nextChar = ' '; // reinitialize
                 while (nextChar != ';') // read and build string until terminator ; found
                 {
                     nextChar = buffer.getChar();
                     firstCharacters.append(nextChar);
                 }
-                if (firstCharacters.toString().contains(MulticastUdpSender.QUIT_SENTINEL)) {
+                if (firstCharacters.toString().contains(MulticastUdpSender.QUIT_SENTINEL)) 
+                {
                     System.out.println("Received sentinel \"" + MulticastUdpSender.QUIT_SENTINEL + "\"");
                     if (!INFINITE_READ_LOOP) {
                         break; // exit out of reading loop
                     }
                 }
-                index = buffer.getInt();
-                firstFloat = buffer.getFloat();
-                secondFloat = buffer.getFloat();
+                boolean foundNumbers = false;
+                String line = firstCharacters.toString();
+                if (line.contains(LINE_TERMINATOR))
+                {
+                    foundNumbers = false;
+                    firstCharacters.setLength(line.length() - LINE_TERMINATOR.length()); // clip EOL sentinel
+                }
+                else if (buffer.hasRemaining()) // likely always true since size is 1500
+                {
+                      messageIndex = buffer.getInt();
+                        firstFloat = buffer.getFloat();
+                       secondFloat = buffer.getFloat();
+                    // simplistic tests for numbers read from buffer
+                    if      ((messageIndex == 0) && (firstFloat == 0.0f) && (secondFloat == 0.0f))
+                              foundNumbers = false;
+                    else if ((messageIndex >= 0) && (messageIndex <= 10000))
+                              foundNumbers = true;
+                }
+                else System.out.print("[trace] no numbers encountered in buffer");
                 buffer.clear();
 
-                if (count < 10) {
-                    System.out.print(" "); // prettier output formatting
+                if (messageCount < 10) {
+                    System.out.print(" "); // prettier output formatting for first nine lines
                 }
-                System.out.print(count + ". \"" + firstCharacters + "\" "); // wrap string in quote marks
-                System.out.println("index=" + index + ", firstFloat=" + firstFloat + " secondFloat=" + secondFloat);
-
-                System.out.println("MulticastReceiver loop complete.");
-                firstCharacters.setLength(0);
+                System.out.println(messageCount + ". \"" + firstCharacters + "\" "); // wrap string in quote marks
+                if (foundNumbers)
+                {
+                    System.out.println("  messageIndex=" + messageIndex + ", firstFloat=" + firstFloat + " secondFloat=" + secondFloat);
+                    System.out.println("  MulticastUdpReceiver message receipt complete.");
+                }
+                firstCharacters.setLength(0); // reset
             }
         } catch (IOException e) {
-            System.err.println("Problem with MulticastReceiver, see exception trace:");
+            System.err.println("Problem with MulticastUdpReceiver, see exception trace:");
             System.err.println(e);
         } finally // clean up after exit condition
         {
@@ -122,7 +151,7 @@ public class MulticastUdpReceiver
                 multicastSocket.close();
             }
             // socket/database/completion cleanup code can go here, if needed.
-            System.out.println("MulticastReceiver finally block, complete.");
+            System.out.println("MulticastUdpReceiver finally block, complete.");
         }
     }
 }