ServiceDiscovery-java

Intro

It's a simple service discovery protocol (like Zeroconf or WS-Discovery) and framework implemented in pure Java. Services are available to publish their :

int port (required)
string type (required)
string title (optional)
byte[] payload (optional)

Usage

Publish service info

// const
private static final String SERVICE_TYPE = "MyServiceType1";
private static final int SERVICE_PORT = 1205;
private static final String SERVICE_TITLE = "Hello world";
public static final byte[] SERVICE_PAYLOAD = new byte[]{1, 2, 3};

private static final String MULTICAST_GROUP = "239.255.255.240";
private static final int MULTICAST_PORT = 4470;

// publish
publisher = new ServicePublisher(MULTICAST_GROUP, MULTICAST_PORT, new ServicePublisher.Listener() {
        @Override
        public void onPublishStarted() {

        }

        @Override
        public void onPublishFinished() {

        }

        @Override
        public boolean acceptServiceRequest(String host, String type, Mode mode) {
            return true; // accept requests from all hosts
        }

        @Override
        public void onNoServiceFound(String host, String type, Mode mode) {

        }

        @Override
        public void onServiceResponseSent(String requestHost, ServiceInfo serviceInfo) {

        }

        @Override
        public void onPublishError(Exception e) {

        }
    });
    publisher.registerService(new ServiceInfo(SERVICE_PORT, SERVICE_TYPE, SERVICE_TITLE, SERVICE_PAYLOAD));
    publisher.start();

Discover services

private static final int RESPONSE_PORT = MULTICAST_PORT + 1;
locator = new ServiceLocator(MULTICAST_GROUP, MULTICAST_PORT, RESPONSE_PORT, new ServiceLocator.Listener() {
    @Override
    public void onDiscoveryStarted() {
        
    }

    @Override
    public void onServiceDiscovered(ServiceInfo serviceInfo, String host) {

    }

    @Override
    public void onDiscoveryFinished() {

    }

    @Override
    public void onDiscoveryError(Exception e) {

    }
});
locator.setMode(Mode.UDP); // response mode (or Mode.TCP)
locator.discoverServices(SERVICE_TYPE);

How it works

Publisher listens for UDP milticast requests from Locator.
Locator starts listening for response (UDP or TCP, depends on locator mode) and sends ServiceRequest with required fields:

string type // service type to discover
Mode mode // TCP or UDP response mode
int port // either TCP or UDP port for response

Publisher receives request, accepts or rejects it (in listener boolean onServiceRequestReceived() or comparing requested and actual service type) and sends ServiceResponse over TCP directly to requester host and port in request (if TCP mode reponse was in request) or UDP multicast response (same UDP group but port in request).
Locator receives response and notifies service is found.

Testing

See DiscoveryTestCase for more information. Average discovery time in my home network is about 60 ms.

How to build

It's built with Maven:

mvn clean install

mvn clean install -DskipTests=true

to build without testing

Implementations

See according Objective-C implementation: https://github.com/4ntoine/ServiceDiscovery-ios

License

Free for non-commercial usage, contact for commercial usage.

Author

Anton Smirnov

dev [at] antonsmirnov [dot] name

2015

iilxy/ServiceDiscovery-java