From 75d96a318905629c9a5cb557c4fd4f430bb45f29 Mon Sep 17 00:00:00 2001 From: "Islas, Sean (Capt)" <sean.islas@nps.edu> Date: Mon, 1 May 2023 10:56:42 -0700 Subject: [PATCH] Add new file --- .../homework2/Islas/UnicastUdpSender.java | 138 ++++++++++++++++++ 1 file changed, 138 insertions(+) create mode 100644 assignments/src/MV3500Cohort2023MarchJune/homework2/Islas/UnicastUdpSender.java diff --git a/assignments/src/MV3500Cohort2023MarchJune/homework2/Islas/UnicastUdpSender.java b/assignments/src/MV3500Cohort2023MarchJune/homework2/Islas/UnicastUdpSender.java new file mode 100644 index 0000000000..c5f10beed4 --- /dev/null +++ b/assignments/src/MV3500Cohort2023MarchJune/homework2/Islas/UnicastUdpSender.java @@ -0,0 +1,138 @@ +package MV3500Cohort2023MarchJune.homework2.Islas; + +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 <a href="https://docs.oracle.com/javase/tutorial/essential/io/datastreams.html">https://docs.oracle.com/javase/tutorial/essential/io/datastreams.html</a> + * @see <a href="https://en.wikipedia.org/wiki/User_Datagram_Protocol">https://en.wikipedia.org/wiki/User_Datagram_Protocol</a> + * @see <a href="https://docs.oracle.com/javase/tutorial/essential/environment/sysprop.html">System properties</a> + * @author mcgredo + * @author brutzman@nps.edu + */ +public class UnicastUdpSender +{ + /** Default constructor */ + public UnicastUdpSender() + { + // default constructor + } + private 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 + /** socket value of shared interest */ + public static final int UDP_PORT = UnicastUdpReceiver.UDP_PORT; // 1415; ensure consistent + private static final int TOTAL_PACKETS_TO_SEND = 25; + + /** socket value of shared interest */ + public static final String DESTINATION_HOST = "localhost"; + // here is what we need for lab comms +// public static final String DESTINATION_HOST = "10.1.105.16"; // localhost 127.0.0.1 or argon 10.1.105.1 or 10.1.105.1 or whatever + + /** + * Program invocation, execution starts here + * @param args command-line arguments + */ + @SuppressWarnings("SleepWhileInLoop") + public static void main(String[] args) + { + 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 Hello MV3500"; // no really + // String padding = new String(); + + try + { + System.out.println(UnicastUdpSender.class.getName() + " shows how to send simple-type values via DataOutputStream"); + System.out.println(UnicastUdpSender.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, UDP_PORT); + + System.out.println("UdpSender address/port: " + destinationAddress.getHostAddress() + "/" + UDP_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(100); // Send packets at rate of one per second + System.out.println(" My guess is: " + packetID + "m/s"); + // System.out.println("[" + UnicastUdpSender.class.getName() + "] " + MY_NAME + " " + sourceAddress + + // " port=" + UDP_PORT + + // " has sent values (" + packetID + "," + value + ",\"" + message + "\"," + isPacketIdEvenParity + + // ")" + padding + " as packet #" + index + " of " + TOTAL_PACKETS_TO_SEND); + baos.reset(); // clear the output stream after sending + } // end for loop + } + 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(); + try + { + if (dos != null) + dos.close(); + } + catch (IOException e) + { + System.err.println("Problem with UdpSender, see exception trace:"); + System.err.println(e); + } + System.out.println(UnicastUdpSender.class.getName() + " complete."); // all done + } + } +} -- GitLab