diff --git a/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonReceivingSendingScreenshots.pdf b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonReceivingSendingScreenshots.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..f8999ad7cd6af4f5270ed9c4c22962ae4057b5ea
Binary files /dev/null and b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonReceivingSendingScreenshots.pdf differ
diff --git a/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpReceiver.java b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpReceiver.java
new file mode 100644
index 0000000000000000000000000000000000000000..dfbb3430f83c30674323d55bd78a063562248eb2
--- /dev/null
+++ b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpReceiver.java
@@ -0,0 +1,92 @@
+package MV3500Cohort2020JulySeptember.homework3.Cannon;
+
+import java.io.*;
+import java.net.*;
+
+/**
+ * An example of receiving UDP packets. Since very often both the
+ * sender and receiver are on the same host we use different ports
+ * for each. This prevents collision complaints from the localhost.
+ *
+ * Start this before launching UdpSender.
+ *
+ * @see https://docs.oracle.com/javase/tutorial/essential/io/datastreams.html
+ * @see https://en.wikipedia.org/wiki/User_Datagram_Protocol
+ * @author mcgredo
+ * @author brutzman
+ */
+public class CannonUdpReceiver
+{
+// public static final int SENDING_PORT = 1414; // port used by UdpSender, unneeded here
+ public static final int RECEIVING_PORT = 1415;
+ public static final String DESINATION_HOST = "localhost";
+
+ /**
+ * @param args the command line arguments
+ * @throws java.io.IOException
+ */
+ public static void main(String[] args) throws IOException
+ {
+ DatagramSocket udpSocket = null;
+
+ try
+ {
+ System.out.println(CannonUdpReceiver.class.getName() + " started...");
+
+ // Create a UDP socket
+ udpSocket = new DatagramSocket(RECEIVING_PORT);
+ udpSocket.setReceiveBufferSize(1500); // how many bytes are in buffer? MTU=1500 is good
+ udpSocket.setBroadcast(false); // we're just receiving here
+
+ byte[] byteArray = new byte[1500];
+ DatagramPacket receivePacket = new DatagramPacket(byteArray, byteArray.length);
+
+ ByteArrayInputStream bais = new ByteArrayInputStream(byteArray);
+ DataInputStream dis = new DataInputStream(bais);
+
+ boolean isEvenParity;
+ int packetCount = 0;
+ int firstInt;
+ float secondFloat;
+ String thirdString;
+ String padding;
+
+ // You need a new receiving packet to read from every packet received
+ while (true)
+ {
+ packetCount++; // good practice to increment counter at start of loop, when possible
+ udpSocket.receive(receivePacket); // blocks until packet is received
+
+ // values of interest follow. order and types of what was sent must match what you are reading!
+ firstInt = dis.readInt(); // packetID
+ secondFloat = dis.readFloat();
+ thirdString = dis.readUTF(); // string value with guaranteed encoding, matches UTF-8 is 8 bit
+ isEvenParity = dis.readBoolean(); // ok, we've gotten everything we're looking for.
+
+ dis.reset(); // now clear the input stream after reading, in preparation for next loop
+
+ if (isEvenParity)
+ padding = " ";
+ else padding = "";
+
+ System.out.println("[" + CannonUdpReceiver.class.getName() + "]" +
+ " packetID=" + firstInt + // have output message use same name as sender
+ ", second float value=" + secondFloat +
+ ", third String value=\"" + thirdString + "\"" + // note that /" is literal quote character
+ " isPacketIdEvenParity=" + isEvenParity + "," + padding +
+ " packet counter=" + packetCount);
+ }
+ }
+ catch(IOException e)
+ {
+ System.err.println("Problem with UdpReceiver, see exception trace:");
+ System.err.println(e);
+ }
+ finally // clean up prior to exit, don't want to leave behind zombie socket
+ {
+ if (udpSocket != null)
+ udpSocket.close();
+ System.out.println(CannonUdpReceiver.class.getName() + " complete."); // all done
+ }
+ }
+}
diff --git a/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpSender.java b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpSender.java
new file mode 100644
index 0000000000000000000000000000000000000000..471f5e0c49b35e0b6ca23906e218d26faf2b6ce9
--- /dev/null
+++ b/assignments/src/MV3500Cohort2020JulySeptember/homework3/Cannon/CannonUdpSender.java
@@ -0,0 +1,115 @@
+package MV3500Cohort2020JulySeptember.homework3.Cannon;
+
+import java.io.*;
+import java.net.*;
+
+/**
+ * An example of sending UDP packets. The sending and receiving programs
+ * use different UDP ports; there can be problems getting this to work
+ * if both the sending and receiving sockets try to use the same port
+ * on the same host.
+ *
+ * Start this before launching UdpReceiver.
+ *
+ * @see https://docs.oracle.com/javase/tutorial/essential/io/datastreams.html
+ * @see https://en.wikipedia.org/wiki/User_Datagram_Protocol
+ * @author mcgredo
+ * @author brutzman
+ */
+public class CannonUdpSender
+{
+ // System properties: https://docs.oracle.com/javase/tutorial/essential/environment/sysprop.html
+ public static final String MY_NAME = System.getProperty("user.name"); // guru incantation 8)
+// public static final int SENDING_PORT = 1414; // not needed, can let system choose an open local port
+ public static final int RECEIVING_PORT = 1415;
+ public static final int TOTAL_PACKETS_TO_SEND = 100;
+
+ // here is what we need for lab comms
+ public static final String DESTINATION_HOST = "10.1.105.7"; // localhost 127.0.0.1 or argon 10.1.105.1 or 10.1.105.1 or whatever
+
+ @SuppressWarnings("SleepWhileInLoop")
+ public static void main(String[] args) throws IOException
+ {
+ DatagramSocket udpSocket = null;
+ DataOutputStream dos = null;
+ int packetID = 0; // counter variable to send in packet
+ float value = -1.0f; // unreachable value is good sentinel to ensure expected changes occur
+ String message = MY_NAME + " says we need to understand llamas in order to code"; // no really
+ String padding = new String();
+
+ try
+ {
+ System.out.println(CannonUdpSender.class.getName() + " shows how to send simple-type values via DataOutputStream");
+ System.out.println(CannonUdpSender.class.getName() + " started...");
+
+ // 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();
+
+ // ID of the host we are sending to
+ InetAddress destinationAddress = InetAddress.getByName(DESTINATION_HOST);
+ // ID of the host we are sending from
+ InetAddress sourceAddress = InetAddress.getByName("localhost"); // possibly identical if source not modified
+
+ DatagramPacket datagramPacket = new DatagramPacket(byteArray, byteArray.length, destinationAddress, RECEIVING_PORT);
+
+ // Hmmm, how fast does UDP stream go? Does UDP effectively slow packets 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? your responsibility.
+
+ for (int index = 1; index <= TOTAL_PACKETS_TO_SEND; index++) // avoid infinite send loops in code, they can be hard to kill!
+ {
+ packetID++; // increment counter, prefer using explicit value to index
+ value = TOTAL_PACKETS_TO_SEND - packetID; // countdown
+ boolean isPacketIdEvenParity = ((packetID % 2) == 0); // % is modulo operator; result 0 is even parity, 1 is odd parity
+
+ // values of interest follow. order and types of what was sent must match what you are reading!
+ dos.writeInt (packetID);
+ dos.writeFloat (value);
+ dos.writeUTF (message); // string value with guaranteed encoding, matches UTF-8 is 8 bit
+ dos.writeBoolean(isPacketIdEvenParity);
+
+ 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.
+// System.out.println("udpSocket output port=" + udpSocket.getLocalPort()); // diagnostic tells what port was chosen by system
+
+ if (isPacketIdEvenParity)
+ padding = " ";
+ else padding = "";
+
+ Thread.sleep(1000); // Send packets at rate of one per second
+ System.out.println("[" + CannonUdpSender.class.getName() + "] " + MY_NAME + " " + sourceAddress +
+ " sent values(" + packetID + "," + value + ",\"" + message + "\"," + isPacketIdEvenParity +
+ ")" + padding + " as packet #" + index + " of " + TOTAL_PACKETS_TO_SEND);
+ baos.reset(); // clear the output stream after sending
+ }
+ }
+ 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();
+ System.out.println(CannonUdpSender.class.getName() + " complete."); // all done
+ }
+ }
+}