Zeroconf

Zeroconf is a simple Java implementation of Multicast DNS Service Discovery, aka the service discovery bit of Zeroconf. Originally written as a quick hack to avoid having to use https://github.com/jmdns/jmdns, it has evolved into something that can both announce and listen for Services:

• Listens on multiple interfaces (IPv4 and IPv6)
• Network topology changes are handled transparently.
• Sent packets include only the A and AAAA records that apply to the interface they're sent on
• Requires Java 8+ and no other dependencies.
• Javadocs at https://faceless2.github.io/zeroconf/docs
• Prebuilt binary at https://faceless2.github.io/zeroconf/dist/zeroconf-1.0.2.jar

Here's a simple example which announces a service on all interfaces on the local machine:

import com.bfo.zeroconf.*;

Zeroconf zc = new Zeroconf();
Service service = new Service.Builder()
                    .setName("MyWeb")
                    .setType("_http._tcp")
                    .setPort(8080)
                    .put("path", "/path/to/service")
                    .build(zc);
service.announce();
// time passes
service.cancel();
// time passes
zc.close();

To set custom TTLs for each mDNS record type:

import com.bfo.zeroconf.*;

Zeroconf zc = new Zeroconf();
Service.Builder builder = new Service.Builder()
                    .setName("MyWeb")
                    .setType("_http._tcp")
                    .setPort(8080)
                    .put("path", "/path/to/service");

// Custom TTLs for each mDNS record type.
int ttl = 120;
builder.setTTL_PTR(ttl);
builder.setTTL_SRV(ttl);
builder.setTTL_TXT(ttl);
builder.setTTL_A(ttl);
builder.build(zc);

// Announce the service.
service.announce();

And to listen, either add a Listener for events or use the live, thread-safe Collection of Services.

import com.bfo.zeroconf.*;

Zeroconf zc = new Zeroconf();
zc.addListener(new ZeroconfListener() {
    public void serviceNamed(String type, String name) {
        if ("_http._tcp".equals(type)) {
            zc.query(type, name);  // Ask for details on any announced HTTP services
        }
    }
    public void serviceAnnounced(Service service) {
        // A new service has just been announced
    }
});

zc.query("_http._tcp", null); // Ask for any HTTP services

// time passes
for (Service s : zc.getServices()) {
  if (s.getType().equals("_http._tcp") {
     // A service has been announced at some point in the past, and has not yet expired.
   }
}

// time passes
zc.close();

To disable IPv6 support, and to only listen on a single network interface with a given IP address, use:

Zeroconf zc = new Zeroconf();
zc.setIPv6(false);
zc.setLocalHostName(ip);

// Add the single NIC with the given IP.
NetworkInterface nic = NetworkUtils.findIPv4NICForIP(ip);
if (nic != null) {
    // Remove all configured NICs.
    zc.getNetworkInterfaces().clear();

    // Add the IPv4 NIC.
    zc.getNetworkInterfaces().add(nic);
}

To build

Run ant to build the Jar in the build directory, and javadoc in the doc directory.