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TCPNumberReceiverUDPResultSender.java 7.17 KiB
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. 
 * @version 08/17/2020
 * @author Goericke
 * @author Weissenberger
 */
public class TCPNumberReceiverUDPResultSender {

    /** Change this to the port where the TCP server is listening */
    public static final int TCP_ARGON_SERVER_PORT = 2317;

    /**
     * @param args 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 input-output error
     */
    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;
    }
}