Post Assignment 2

projects/Assignments/homework2/AngelMulticastReceiver.java

+
+
+
+import java.io.*;
+import java.net.*;
+
+/**
+ *
+ * @author mcgredo
+ */
+public class AngelMulticastReceiver {
+
+    public static final String MULTICAST_ADDRESS = "239.1.2.15";
+    public static final int DESTINATION_PORT = 1717;
+    /** How many routers can be crossed */
+    public static final int TTL = 10; 
+    
+    public static void main(String[] args) 
+    {
+        try
+        {
+        
+            // This is a java/IPv6 problem. You should also add it to the
+            // arguments used to start the app, eg -Djava.net.preferIPv4Stack=true
+            // set in the "run" section of preferences. Also, typically
+            // netbeans must be restarted after these settings.
+            // https://stackoverflow.com/questions/18747134/getting-cant-assign-requested-address-java-net-socketexception-using-ehcache
+            System.setProperty("java.net.preferIPv4Stack", "true");
+            
+            
+            MulticastSocket multicastSocket = new MulticastSocket(DESTINATION_PORT);
+            multicastSocket.setTimeToLive(TTL);
+            InetAddress multicastAddress = InetAddress.getByName(MULTICAST_ADDRESS);
+            System.out.println(multicastAddress);            
+            // Join group useful on receiving side
+            multicastSocket.joinGroup(multicastAddress);
+            // You can join multiple groups here
+            while(true)
+            {
+                byte[] packetArray = new byte[1500];
+                DatagramPacket packet = new DatagramPacket(packetArray, packetArray.length);
+                multicastSocket.receive(packet);
+                ByteArrayInputStream bais = new ByteArrayInputStream(packet.getData());
+                DataInputStream dis = new DataInputStream(bais);
+                char type = dis.readChar();
+                if (type == 'A') {
+                    float firstNumber = dis.readFloat();
+                    float secondNumber = dis.readFloat();
+                    float thirdNumber = dis.readFloat();
+                    System.out.println("Abrams POS: (x: " + firstNumber + ", y: " + secondNumber +", z: " + thirdNumber + " )");    
+                }
+                if (type == 'B') {
+                    int lngth = dis.readInt();
+                    String informationLine = "";
+                    for(int i=0; i<lngth; i++) {
+                        informationLine += dis.readChar();
+                    }
+                    System.out.println(informationLine);
+                }
+            }   
+        }
+        catch(Exception e)
+        {
+            System.out.println(e);
+        }
+    }
+    
+}

projects/Assignments/homework2/AngelMulticastSenderExample.java

+
+
+
+import java.io.*;
+import java.net.*;
+import java.util.Random;
+
+/**
+ * Looks a lot like a UDP sender.
+ * 
+ * @author mcgredo
+ */
+public class AngelMulticastSenderExample {
+
+    public static final String MULTICAST_ADDRESS = "239.1.2.15";
+    public static final int DESTINATION_PORT = 1717;
+    /** How many routers can be crossed */
+    public static final int TTL = 10; 
+    
+    public static void main(String[] args) 
+    {
+        try
+        {
+            // This is a java/IPv6 problem. You should also add it to the
+            // arguments used to start the app, eg -Djava.net.preferIPv4Stack=true
+            // set in the "run" section of preferences. Also, typically
+            // netbeans must be restarted after these settings.
+            // https://stackoverflow.com/questions/18747134/getting-cant-assign-requested-address-java-net-socketexception-using-ehcache
+            System.setProperty("java.net.preferIPv4Stack", "true");
+            
+            
+            MulticastSocket multicastSocket = new MulticastSocket(1718);
+            multicastSocket.setTimeToLive(TTL);
+            InetAddress multicastAddress = InetAddress.getByName(MULTICAST_ADDRESS);
+            System.out.println(multicastAddress);            
+            // Join group useful on receiving side
+            multicastSocket.joinGroup(multicastAddress);
+            // You can join multiple groups here
+            
+            // Put together a message with binary content. "ByteArrayOutputStream"
+            // is a java.io utility that lets us put together an array of binary
+            // data, which we put into the UDP packet.
+            
+            ByteArrayOutputStream baos = new ByteArrayOutputStream();
+            DataOutputStream dos = new DataOutputStream(baos);
+            Random randomFLT = new Random();
+            Random rndFLT = new Random();
+            for(int idx = 0; idx < 100; idx++){
+                float flt = rndFLT.nextFloat();
+                if (flt <=.5){
+                    dos.writeChars("A");
+                    dos.writeFloat(randomFLT.nextFloat()*100);
+                    dos.writeFloat(randomFLT.nextFloat()*100);
+                    dos.writeFloat(randomFLT.nextFloat()*100);
+                }
+                else if (flt < .8 ) {
+                    dos.writeChars("B");
+                    dos.writeInt("Information Bravo.".length());
+                    dos.writeChars("Information Bravo.");
+                }
+                else {
+                    dos.writeChars("B");
+                    dos.writeInt("Information Charlie.".length());
+                    dos.writeChars("Information Charlie.");
+                }
+            byte[] buffer = baos.toByteArray();
+            // Put together a packet to send
+            
+            // muticast group we are sending to--not a single host
+            
+                DatagramPacket packet = new DatagramPacket(buffer, buffer.length, multicastAddress, DESTINATION_PORT);
+       
+            // How fast does this go? Does UDP try to slow it down, or does
+            // this cause network problems? (hint: yes for an unlimited send
+            // rate, unlike TCP). How do you know on the receiving side
+            // that you haven't received a duplicate UDP packet, out of
+            // order packet, or dropped packet?
+            
+
+               multicastSocket.send(packet);
+               baos.reset();
+               Thread.sleep(1000); // Send 100, one per second
+               System.out.println("Sent multicast packet " + idx + " of 100");
+            }
+        }
+        catch(Exception e)
+        {
+            System.out.println(e);
+        }
+    }
+    
+}