Commit TCPNumberReceiverUDPResultSender for HW #3

08/17/2020

assignments/src/MV3500Cohort2020JulySeptember/homework3/Goericke/TCPNumberReceiverUDPResultSender.java

+package MV3500Cohort2020JulySeptember.homework3.Goericke;
+
+import java.io.BufferedReader;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
+
+/**
+ * This class will be connected by an TCP sender over VPN (argon), calculating 
+ * a result of an equation and send the result back via UDP over VPN. 
+ * @date 08/17/2020
+ * @group Goericke/Weissenberger
+ */
+public class TCPNumberReceiverUDPResultSender {
+
+    // Change this to the port where the TCP server is listening
+    private static final int TCP_ARGON_SERVER_PORT = 2317;
+
+    /**
+     * @param args the command line arguments
+     */
+    public static void main(String[] args) {
+        try {
+            
+            // ServerSocket waits for a connection from a client. 
+            System.out.println("TCPNumberReceiver has started...");
+            ServerSocket serverSocket = new ServerSocket(TCP_ARGON_SERVER_PORT);
+            InetAddress remoteAddress;
+            
+            // declare the stream and readers
+            InputStream inputStream;
+            InputStreamReader inputStreamReader;
+            BufferedReader bufferedReader;
+            
+            // declare needed variables
+            String clientMessage;
+            int number1, number2;
+            String calculation_Method;
+            int iUDPResultReceivingPort;
+            // Server is up and waiting (i.e. "blocked" or paused)
+            // Loop, infinitely, waiting for client connections.
+            while (true) { 
+                
+                // block until connected to a client
+                try (Socket clientConnectionSocket = serverSocket.accept())
+                {
+                    // Now hook everything up (i.e. set up the streams), Java style:
+                    inputStream  = clientConnectionSocket.getInputStream();
+                    inputStreamReader = new InputStreamReader(inputStream);
+                    bufferedReader  = new BufferedReader(inputStreamReader);
+                    
+                    // get the date from TCP packet
+                    clientMessage = bufferedReader.readLine();
+                    number1 = Integer.parseInt(bufferedReader.readLine());
+                    number2 = Integer.parseInt(bufferedReader.readLine());
+                    calculation_Method = bufferedReader.readLine();
+                    iUDPResultReceivingPort = Integer.parseInt(bufferedReader.readLine());
+                    
+                    // print them out (for debugging)
+                    System.out.println("Message recived: "+clientMessage);
+                    System.out.println("Number 1 recived: "+number1);
+                    System.out.println("Number 2 recived: "+number2);
+                    System.out.println("Calc Method recived: "+calculation_Method);
+                    System.out.println("Send result to port: "+iUDPResultReceivingPort);
+                    // get the sender IP (is used for sending UDP)
+                    remoteAddress = clientConnectionSocket.getInetAddress();
+                    
+                    System.out.println("Send result to IP: "+remoteAddress.getHostAddress());
+                    
+                    // try to send the calculated result as a float via UDP...
+                    sendResultViaUDP(calculateResult(number1, number2, calculation_Method), remoteAddress, iUDPResultReceivingPort);
+                }
+            }
+        } catch (IOException e) {
+            System.err.println("Problem with TcpExample3Server 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.err.println("*** Be sure to stop any other running instances of programs using this port!");
+            }
+        }
+    }
+    
+    /**
+     * send the result to Bernd 10x
+     * @param result
+     * @param inetAddress Bernd's IP
+     * @param port Bernd's UDP port number
+     * @throws IOException 
+     */
+    private static void sendResultViaUDP(float result, InetAddress inetAddress, int port) throws IOException{
+        DatagramSocket udpSocket = null;
+        DataOutputStream  dos = null;
+        
+        try
+        {
+            // Create a UDP socket
+            udpSocket = new DatagramSocket(); // let system assign output port, then SENDING_PORT not needed
+            
+            // 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(1500); // how many bytes are in buffer?  MTU=1500 is good
+            dos = new DataOutputStream(baos); // wrapper for writing values, connects both streams
+			
+            // Put together a packet to send
+            // these types and order of variables must match on sender and receiver
+            byte[] byteArray = baos.toByteArray();
+            
+            DatagramPacket datagramPacket = new DatagramPacket(byteArray, byteArray.length, inetAddress, port);
+       
+            for (int index = 1; index <= 10; index++) 
+            {
+                dos.writeFloat  (result);
+                dos.flush(); // sends DataOutputStream to ByteArrayOutputStream
+                byteArray = baos.toByteArray();    // OK so go get the flushed result...
+                datagramPacket.setData(byteArray); // and put it in the packet...
+                udpSocket.send(datagramPacket);    // and send it away. boom gone, nonblocking.
+            
+                Thread.sleep(1000); // Send packets at rate of one per second
+                baos.reset(); // clear the output stream after sending
+            }
+            dos.close();
+        }
+        catch (IOException | InterruptedException e)
+        {
+            System.err.println("Problem with UdpSender, see exception trace:");
+            System.err.println(e);
+        } 
+        finally // clean up prior to exit, don't want to leave behind zombies
+        {
+            if (udpSocket != null)
+                udpSocket.close();
+            
+            if (dos != null)
+                dos.close();
+        }
+    }
+    
+    /**
+     * calculates the result based on given numbers and operator
+     * @param n1 first number
+     * @param n2 second number
+     * @param operator
+     * @return the result as a float
+     */
+    private static float calculateResult(int n1, int n2, String operator){
+        float result = -1;
+        switch (operator) {
+            case "+":
+                result = n1 + n2;
+                break;
+            case "-":
+                result = n1 - n2;
+                break;
+            case "*":
+                result = n1 * n2;
+                break;
+            case "/":
+                result = n1 / n2;
+                break;
+            default:
+                System.err.println(operator +" is not a valid operator!");
+                break;
+        }
+        return result;
+    }
+}