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An open source implementation of the Distributed Interactive Simulation (DIS) IEEE-1278 protocol
package edu.nps.moves.examples;
import java.io.*;
import java.net.*;
import java.util.*;
import edu.nps.moves.dis.*;
import edu.nps.moves.disutil.CoordinateConversions;
import edu.nps.moves.disutil.DisTime;
/**
* Creates and sends ESPDUs in IEEE binary format.
*
* @author DMcG
*/
public class EspduSender
{
public enum NetworkMode{UNICAST, MULTICAST, BROADCAST};
/** default multicast group we send on */
public static final String DEFAULT_MULTICAST_GROUP="239.1.2.3";
/** Port we send on */
public static final int PORT = 62040;
/** Possible system properties, passed in via -Dattr=val
* networkMode: unicast, broadcast, multicast
* destinationIp: where to send the packet. If in multicast mode, this can be mcast.
* To determine bcast destination IP, use an online bcast address
* caclulator, for example http://www.remotemonitoringsystems.ca/broadcast.php
* If in mcast mode, a join() will be done on the mcast address.
* port: port used for both source and destination.
* @param args
*/
public static void main(String args[])
{
/** an entity state pdu */
EntityStatePdu espdu = new EntityStatePdu();
MulticastSocket socket = null;
DisTime disTime = DisTime.getInstance();
// ICBM coordinates for my office
double lat = 36.595517;
double lon = -121.877000;
// Default settings. These are used if no system properties are set.
// If system properties are passed in, these are over ridden.
int port = PORT;
NetworkMode mode = NetworkMode.MULTICAST;
InetAddress destinationIp = null;
try
{
destinationIp = InetAddress.getByName(DEFAULT_MULTICAST_GROUP);
}
catch(Exception e)
{
System.out.println(e + " Cannot create multicast address");
System.exit(0);
}
// All system properties, passed in on the command line via -Dattribute=value
Properties systemProperties = System.getProperties();
// IP address we send to
String destinationIpString = systemProperties.getProperty("destinationIp");
// Port we send to, and local port we open the socket on
String portString = systemProperties.getProperty("port");
// Network mode: unicast, multicast, broadcast
String networkModeString = systemProperties.getProperty("networkMode"); // unicast or multicast or broadcast
// Set up a socket to send information
try
{
// Port we send to
if(portString != null)
port = Integer.parseInt(portString);
socket = new MulticastSocket(port);
// Where we send packets to, the destination IP address
if(destinationIpString != null)
{
destinationIp = InetAddress.getByName(destinationIpString);
}
// Type of transport: unicast, broadcast, or multicast
if(networkModeString != null)
{
if(networkModeString.equalsIgnoreCase("unicast"))
mode = NetworkMode.UNICAST;
else if(networkModeString.equalsIgnoreCase("broadcast"))
mode = NetworkMode.BROADCAST;
else if(networkModeString.equalsIgnoreCase("multicast"))
{
mode = NetworkMode.MULTICAST;
if(!destinationIp.isMulticastAddress())
{
throw new RuntimeException("Sending to multicast address, but destination address " + destinationIp.toString() + "is not multicast");
}
socket.joinGroup(destinationIp);
}
} // end networkModeString
}
catch(Exception e)
{
System.out.println("Unable to initialize networking. Exiting.");
System.out.println(e);
System.exit(-1);
}
// Initialize values in the Entity State PDU object. The exercise ID is
// a way to differentiate between different virtual worlds on one network.
// Note that some values (such as the PDU type and PDU family) are set
// automatically when you create the ESPDU.
espdu.setExerciseID((short)1);
// The EID is the unique identifier for objects in the world. This
// EID should match up with the ID for the object specified in the
// VMRL/x3d/virtual world.
EntityID eid = espdu.getEntityID();
eid.setSite(0);
eid.setApplication(1);
eid.setEntity(2);
// Set the entity type. SISO has a big list of enumerations, so that by
// specifying various numbers we can say this is an M1A2 American tank,
// the USS Enterprise, and so on. We'll make this a tank. There is a
// separate project elsehwhere in this project that implements DIS
// enumerations in C++ and Java, but to keep things simple we just use
// numbers here.
EntityType entityType = espdu.getEntityType();
entityType.setEntityKind((short)1); // Platform (vs lifeform, munition, sensor, etc.)
entityType.setCountry(225); // USA
entityType.setDomain((short)1); // Land (vs air, surface, subsurface, space)
entityType.setCategory((short)1); // Tank
entityType.setSubcategory((short)1); // M1 Abrams
entityType.setSpec((short)3); // M1A2 Abrams
// Loop through sending 100 ESPDUs
try
{
System.out.println("Sending 100 ESPDU packets to " + destinationIp.toString());
for(int idx = 0; idx < 100; idx++)
{
// DIS time is a pain in the ass. DIS time units are 2^31-1 units per
// hour, and time is set to DIS time units from the top of the hour.
// This means that if you start sending just before the top of the hour
// the time units can roll over to zero as you are sending. The receivers
// (escpecially homegrown ones) are often not able to detect rollover
// and may start discarding packets as dupes or out of order. We use
// an NPS timestamp here, hundredths of a second since the start of the
// year. The DIS standard for time is often ignored in the wild; I've seen
// people use Unix time (seconds since 1970) and more. Or you can
// just stuff idx into the timestamp field to get something that is monotonically
// increasing.
// Note that timestamp is used to detect duplicate and out of order packets.
// That means if you DON'T change the timestamp, many implementations will simply
// discard subsequent packets that have an identical timestamp. Also, if they
// receive a PDU with an timestamp lower than the last one they received, they
// may discard it as an earlier, out-of-order PDU. So it is a good idea to
// update the timestamp on ALL packets sent.
//espdu.setTimestamp(disTime.getNpsTimestamp());
// An alterative approach: actually follow the standard. It's a crazy concept,
// but it might just work.
int ts = disTime.getDisAbsoluteTimestamp();
espdu.setTimestamp(ts);
// Set the position of the entity in the world. DIS uses a cartesian
// coordinate system with the origin at the center of the earth, the x
// axis out at the equator and prime meridian, y out at the equator and
// 90 deg east, and z up and out the north pole. To place an object on
// the earth's surface you also need a model for the shape of the earth
// (it's not a sphere.) All the fancy math necessary to do this is in
// the SEDRIS SRM package. There are also some one-off formulas for
// doing conversions from, for example, lat/lon/altitude to DIS coordinates.
// Here we use those one-off formulas.
// Modify the position of the object. This will send the object a little
// due east by adding some to the longitude every iteration. Since we
// are on the Pacific coast, this sends the object east. Assume we are
// at zero altitude. In other worlds you'd use DTED to determine the
// local ground altitude at that lat/lon, or you'd just use ground clamping.
// The x and y values will change, but the z value should not.
lon = lon + (double)((double)idx / 1000.0);
System.out.println("lla=" + lat + "," + lon + ", 0.0");
double disCoordinates[] = CoordinateConversions.getXYZfromLatLonDegrees(lat, lon, 0.0);
Vector3Double location = espdu.getEntityLocation();
location.setX(disCoordinates[0]);
location.setY(disCoordinates[1]);
location.setZ(disCoordinates[2]);
// Optionally, we can do some rotation of the entity
/*
Orientation orientation = espdu.getEntityOrientation();
float psi = orientation.getPsi();
psi = psi + idx;
orientation.setPsi(psi);
orientation.setTheta((float)(orientation.getTheta() + idx /2.0));
*/
// You can set other ESPDU values here, such as the velocity, acceleration,
// and so on.
// Marshal out the espdu object to a byte array, then send a datagram
// packet with that data in it.
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
espdu.marshal(dos);
// The byte array here is the packet in DIS format. We put that into a
// datagram and send it.
byte[] data = baos.toByteArray();
DatagramPacket packet = new DatagramPacket(data, data.length, destinationIp, PORT);
socket.send(packet);
// Send every 1 sec. Otherwise this will be all over in a fraction of a second.
Thread.sleep(1000);
location = espdu.getEntityLocation();
System.out.print("Espdu #" + idx + " EID=[" + eid.getSite() + "," + eid.getApplication() + "," + eid.getEntity() + "]");
System.out.print(" DIS coordinates location=[" + location.getX() + "," + location.getY() + "," + location.getZ() + "]");
double c[] = {location.getX(), location.getY(), location.getZ()};
double lla[] = CoordinateConversions.xyzToLatLonDegrees(c);
System.out.println(" Location (lat/lon/alt): [" + lla[0] + ", " + lla[1] + ", " + lla[2] + "]");
}
}
catch(Exception e)
{
System.out.println(e);
}
}
}