41 | * private final ABLock selectorLock = new ABLock();
42 | *
43 | * ...
44 | *
45 | * // Channel registration
46 | * selectorLock.lockA1();
47 | * try {
48 | * getSelector().wakeup();
49 | * selectorLock.lockA2();
50 | * try {
51 | * channels.put(nic, channel.register(getSelector(), SelectionKey.OP_READ));
52 | * } finally {
53 | * selectorLock.unlockA2();
54 | * }
55 | * } finally {
56 | * selectorLock.unlockA1();
57 | * }
58 | *
59 | * ...
60 | *
61 | * // Select
62 | * Selector selector = getSelector();
63 | * selectorLock.lockB();
64 | * try {
65 | * selector.select();
66 | * } finally {
67 | * selectorLock.unlockB();
68 | * }
69 | *
70 | * 25 | * This is the root class for the Service Discovery object. 26 | *
27 | * This class does not have any fancy hooks to clean up. The {@link #close} method should be called when the 28 | * class is to be discarded, but failing to do so won't break anything. Announced services will expire in 29 | * their own time, which is typically two minutes - although during this time, conforming implementations 30 | * should refuse to republish any duplicate services. 31 | *
32 | */ 33 | @SuppressWarnings({"unused", "WeakerAccess"}) 34 | public final class Zeroconf implements Closeable { 35 | private static final String DISCOVERY = "_services._dns-sd._udp.local"; 36 | private static final InetSocketAddress BROADCAST4; 37 | private static final InetSocketAddress BROADCAST6; 38 | private static final Logger LOGGER = LoggerFactory.getLogger(Zeroconf.class); 39 | 40 | static { 41 | try { 42 | BROADCAST4 = new InetSocketAddress(InetAddress.getByName("224.0.0.251"), 5353); 43 | BROADCAST6 = new InetSocketAddress(InetAddress.getByName("FF02::FB"), 5353); 44 | } catch (IOException ex) { 45 | throw new IllegalStateException(ex); 46 | } 47 | } 48 | 49 | private final ListenerThread thread; 50 | private final List178 | * Add a {@link NetworkInterface} to the list of interfaces that send and received Service 179 | * Discovery Packets. The interface should be up, should 180 | * {@link NetworkInterface#supportsMulticast} support Multicast and not be a 181 | * {@link NetworkInterface#isLoopback Loopback interface}. However, adding a 182 | * NetworkInterface that does not match this requirement will not throw an Exception - it 183 | * will just be ignored, as will any attempt to add a NetworkInterface that has already 184 | * been added. 185 | *
186 | * All the interface's IP addresses will be added to the list of 187 | * {@link #getLocalAddresses local addresses}. 188 | * If the interface's addresses change, or the interface is otherwise modified in a 189 | * significant way, then it should be removed and re-added to this object. This is 190 | * not done automatically. 191 | *
192 | * 193 | * @param nic a NetworkInterface 194 | * @return this 195 | * @throws IOException if something goes wrong in an I/O way 196 | */ 197 | @NotNull 198 | public Zeroconf addNetworkInterface(@NotNull NetworkInterface nic) throws IOException { 199 | thread.addNetworkInterface(nic); 200 | return this; 201 | } 202 | 203 | @NotNull 204 | public Zeroconf addNetworkInterfaces(@NotNull Collection
227 | * for (Enumeration<NetworkInterface> e = NetworkInterface.getNetworkInterfaces();e.hasMoreElements();) {
228 | * addNetworkInterface(e.nextElement());
229 | * }
230 | *
231 | *
232 | * @return this
233 | * @throws IOException if something goes wrong in an I/O way
234 | */
235 | @NotNull
236 | public Zeroconf addAllNetworkInterfaces() throws IOException {
237 | for (EnumerationInetAddress.getLocalHost().getHostName().
267 | *
268 | * @return the local host name
269 | */
270 | public String getLocalHostName() {
271 | if (hostname == null) throw new IllegalStateException("Hostname cannot be determined");
272 | return hostname;
273 | }
274 |
275 | /**
276 | * Set the local hostname, as returned by {@link #getOrCreateLocalHostName}
277 | *
278 | * @param name the hostname, which should be undotted
279 | * @return this
280 | */
281 | @NotNull
282 | public Zeroconf setLocalHostName(@NotNull String name) {
283 | this.hostname = name;
284 | return this;
285 | }
286 |
287 | /**
288 | * Return a list of InetAddresses which the Zeroconf object considers to be "local". These
289 | * are the all the addresses of all the {@link NetworkInterface} objects added to this
290 | * object. The returned list is a copy, it can be modified and will not be updated
291 | * by this object.
292 | *
293 | * @return a List of local {@link InetAddress} objects
294 | */
295 | public List329 | * This is largely derived from other implementations, but broadly the logic here is 330 | * that questions are matched against records based on the "name" and "type" fields, 331 | * where {@link #DISCOVERY} and {@link Record#TYPE_ANY} are wildcards for those 332 | * fields. Currently we match against all packet types - should these be just "PTR" 333 | * records? 334 | *
335 | * Once we have this list of matched records, we search this list for any PTR records 336 | * and add any matching SRV or TXT records (RFC 6763 12.1). After that, we scan our 337 | * updated list and add any A or AAAA records that match any SRV records (12.2). 338 | *
339 | * At the end of all this, if we have at least one record, send it as a response
340 | */
341 | private void handlePacket(@NotNull Packet packet) {
342 | Packet response = null;
343 | Set
423 | * The approach is borrowed from https://www.npmjs.com/package/bonjour - we send three
424 | * broadcasts trying to match the service name, 250ms apart. If we receive no response,
425 | * assume there is no service that matches
426 | *
427 | * Note the approach here is the only example of where we send a query packet. It could
428 | * be used as the basis for us acting as a service discovery client
429 | *
430 | * @param fqdn the fully qualified service name, eg "My Web Service._http._tcp.local".
431 | */
432 | private boolean probe(final String fqdn) {
433 | Packet probe = new Packet();
434 | probe.setResponse(false);
435 | probe.addQuestion(new RecordANY(fqdn));
436 | AtomicBoolean match = new AtomicBoolean(false);
437 | PacketListener probeListener = packet -> {
438 | if (packet.isResponse()) {
439 | for (Record r : packet.getAnswers()) {
440 | if (r.getName().equalsIgnoreCase(fqdn)) {
441 | synchronized (match) {
442 | match.set(true);
443 | match.notifyAll();
444 | }
445 | }
446 | }
447 |
448 | for (Record r : packet.getAdditionals()) {
449 | if (r.getName().equalsIgnoreCase(fqdn)) {
450 | synchronized (match) {
451 | match.set(true);
452 | match.notifyAll();
453 | }
454 | }
455 | }
456 | }
457 | };
458 |
459 | addReceiveListener(probeListener);
460 | for (int i = 0; i < 3 && !match.get(); i++) {
461 | send(probe);
462 | synchronized (match) {
463 | try {
464 | match.wait(250);
465 | } catch (InterruptedException ex) {
466 | // ignore
467 | }
468 | }
469 | }
470 |
471 | removeReceiveListener(probeListener);
472 | return match.get();
473 | }
474 |
475 | /**
476 | * Announce the service - probe to see if it already exists and fail if it does, otherwise
477 | * announce it
478 | */
479 | public void announce(@NotNull Service service) {
480 | if (service.getDomain() == null) service.setDomain(getDomain());
481 | if (service.getHost() == null) service.setHost(getLocalHostName());
482 | if (!service.hasAddresses()) service.addAddresses(getLocalAddresses());
483 |
484 | Packet packet = service.getPacket();
485 | if (probe(service.getInstanceName()))
486 | throw new IllegalArgumentException("Service " + service.getInstanceName() + " already on network");
487 |
488 | getRegistry().addAll(packet.getAnswers());
489 | services.add(service);
490 |
491 | for (int i = 0; i < 3; i++) {
492 | send(packet);
493 |
494 | try {
495 | Thread.sleep(225);
496 | } catch (InterruptedException ignored) {
497 | }
498 | }
499 |
500 | LOGGER.info("Announced {}.", service);
501 | }
502 |
503 | /**
504 | * Unannounce the service. Do this by re-announcing all our records but with a TTL of 0 to
505 | * ensure they expire. Then remove from the registry.
506 | */
507 | public void unannounce(@NotNull Service service) {
508 | Packet packet = service.getPacket();
509 | getRegistry().removeAll(packet.getAnswers());
510 | for (Record r : packet.getAnswers()) {
511 | getRegistry().remove(r);
512 | r.setTTL(0);
513 | }
514 |
515 | services.remove(service);
516 |
517 | for (int i = 0; i < 3; i++) {
518 | send(packet);
519 |
520 | try {
521 | Thread.sleep(125);
522 | } catch (InterruptedException ignored) {
523 | }
524 | }
525 |
526 | LOGGER.info("Unannounced {}.", service);
527 | }
528 |
529 | public class DiscoveredServices implements Runnable {
530 | private final String serviceName;
531 | private final PacketListener listener;
532 | private final Set