Multicast DNS (mDNS) & DNS-Based Service Discovery (DNS-SD) in Java Introduction The Multicast DNS (mDNS) [RFC 6762] & DNS-Based Service Discovery (DNS-SD) [RFC 6763 in Java, mdnsjava for short, project is an extension of the dnsjava [dnsjava.org] project that implements Multicast DNS (mDNS) [RFC 6762] and DNS-Based Service Discovery (DNS-SD) [RFC 6763] in Java (aka. Bonjour in Java). mdnsjava does not artificially bind the mDNS and DNS-based Service Discovery functionality into a single combined API, instead, treating each as a separate function, independent from, but related to, the other. Thus, allowing clients to use Multicast DNS (mDNS) [RFC 6762] as a substitute for DNS and not just for service discovery.

Features, Version 2.1.5 Multicast DNS (mDNS) Responder Multicast DNS (mDNS) Querier Service Registration/Unregistration Browsing for Services Browsing for DNS/mDNS Resource Records Resolving/Looking up Services synchronously and asynchronously Resolving/Looking up DNS/mDNS Resource Records synchronously and asynchronously Tested with dnsjava versions 2.1.4, 2.1.5, and 2.1.6. Dependencies This project depends on:

dnsjava.org project, version 2.1.5 or higher. (may work with early versions) Java SE 1.5 or higher Command Line Tool Usage $java -jar mdnsjava.jar dnssd

Command Line: dnssd [parameters]

dnssd -E (Enumerate recommended registration domains) dnssd -F (Enumerate recommended browsing domains) dnssd -B [] (Browse for services instances) dnssd -L [] (Look up a service instance) dnssd -R [...] (Register a service) dnssd -Q (Generic query for any record type) dnssd -G v4/v6/v4v6 (Get address information for hostname) dnssd -V (Get version of currently running daemon / system service) $

API Usage Browse for Browse and Registration Domains using the default DNS search path.

Resolve resolve = new Resolve(MulticastDNSService.DEFAULT_REGISTRATION_DOMAIN_NAME, MulticastDNSService.REGISTRATION_DOMAIN_NAME, MulticastDNSService.DEFAULT_BROWSE_DOMAIN_NAME, MulticastDNSService.BROWSE_DOMAIN_NAME, MulticastDNSService.LEGACY_BROWSE_DOMAIN_NAME); Domain[] domains = resolve.resolveDomains(); for (Domain domain : domains) { System.out.println(domain); } resolve.close();

Browsing for Services. Receiving events for each service discovered and removed. Browse browse = new Browse(serviceTypes); browse.start(new DNSSDListener() { public void serviceDiscovered(Object id, ServiceInstance service) { System.out.println("Service Discovered - " + service); }

 public void serviceRemoved(Object id, ServiceInstance service)
 {
     System.out.println("Service Removed - " + service);
 }

public void handleException(Object id, Exception e)
 {
     System.err.println("Exception: " + e.getMessage());
     e.printStackTrace(System.err);
 }

}); while (true) { Thread.sleep(10); if (System.in.read() == 'q') { break; } } browse.close();

Resolve (Lookup) a Service, (one shot synchronously). Resolve resolve = new Resolve("Test._mdc._tcp.local."); ServiceInstance[] services = resolve.resolveServices(); for (ServiceInstance service : services) { System.out.println(service); }

Resolve (Lookup) a Records, (one shot synchronously). Resolve resolve = new Resolve("Test._mdc._tcp.local.", Type.ANY, DClass.IN); Record[] records = resolve.resolveRecords(); for (Record record : records) { System.out.println(records); }

Resolve (Lookup) a Records asynchronously, (one shot asynchronously). Resolve resolve = new Resolve("Test._mdc._tcp.local.", Type.ANY, DClass.IN); Record[] records = resolve.resolveRecordsAsych(new RecordListener() { public void receiveRecord(Object id, Record record) { System.out.println("Record Found - " + record); }

public void handleException(Object id, Exception e)
 {
     System.err.println("Exception: " + e.getMessage());
     e.printStackTrace(System.err);
 }

}); Thread.sleep(1000); resolve.close();

Register and Unregister a Service MulticastDNSService mDNSService = new MulticastDNSService(); ServiceInstance service = new ServiceInstance(serviceName, 0, 0, port, hostname, MulticastDNSService.DEFAULT_SRV_TTL, addresses, txtValues); ServiceInstance registeredService = mDNSService.register(service); if (registeredService != null) { System.out.println("Services Successfully Registered: \n\t" + registeredService); } else { System.err.println("Services Registration Failed!"); } while (true) { Thread.sleep(10); if (System.in.read() == 'q') { if (mDNSService.unregister(registeredService)) { System.out.println("Services Successfully Unregistered: \n\t" + service); } else { System.err.println("Services Unregistration Failed!"); } break; } } mDNSService.close();

Workaround for Java IPv6 Issues Numerous bugs have been reported with Java's support of IPv6. Among them is an issue where the IP header's Time To Live (TTL) value for datagrams does not get set properly. If the IP header's Time To Live (TTL) value is not set to 255, then the Java VM must be started with IPv6 disabled, using the "-Djava.net.preferIPv4Stack=true" VM option. This is true for IPv4 datagrams as well. Disabling IPv6 fixes the TTL issue for IPv4.

For Example:

java -Djava.net.preferIPv4Stack=true -jar mdnsjava.jar dnssd -E

SMPTE ST2071 Media & Device Control over IP This project was originally created for the development of a proofing of concept application for the Society of Motion Picture and Television Engineers (SMPTE) suite of standards on Media & Device Control over IP networks, [SMPTE ST2071]. The SMPTE ST2071 suite of standards defines an open standard for the representation of devices and services within an Internet of Things (IoT) and defines extensions to the DNS-SD protocol that allows for the service discovery DNS infrastructure to differ from the DNS infrastructure used by clients for name resolution.