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projects/Assignments/homework2/SasalaMulticastReceiver.java

+
+
+
+import java.io.*;
+import java.net.*;
+
+/**
+ *
+ * @author mcgredo
+ */
+public class SasalaMulticastReceiver {
+
+    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);
+                float temperature = dis.readFloat();
+                String DTG = dis.readLine();
+                
+                System.out.println("Time: " + DTG + " Temperature:" + temperature);
+            }
+        }
+        catch(Exception e)
+        {
+            System.out.println(e);
+        }
+    }
+    
+}

projects/Assignments/homework2/SasalaMulticastSender.java

+
+
+
+import java.io.*;
+import java.net.*;
+import java.time.LocalDateTime;
+
+/**
+ * Looks a lot like a UDP sender.
+ * 
+ * @author mcgredo
+ */
+public class SasalaMulticastSender {
+
+    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);
+            
+            for(int idx = 0; idx < 100; idx++)
+            {
+                double temperature = 100 * Math.random();
+                LocalDateTime LDT =  LocalDateTime.now();
+                String time = LDT.toString();
+            
+                dos.writeFloat((float) temperature);
+                dos.writeChars(time);
+            
+                // Put together a packet to send
+                // muticast group we are sending to--not a single host
+                byte[] buffer = baos.toByteArray();
+                DatagramPacket packet = new DatagramPacket(buffer, buffer.length, multicastAddress, DESTINATION_PORT);
+                
+                multicastSocket.send(packet);
+                Thread.sleep(1000); // Send 100, one per second
+                System.out.println("Sent multicast packet " + idx + " of 100");
+                
+                baos.reset();
+            }
+        }
+        catch(Exception e)
+        {
+            System.out.println(e);
+        }
+    }
+    
+}