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)
// 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();
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);
- Publisher listens for UDP milticast requests from Locator.
- Locator starts listening for response (UDP or TCP, depends on locator
mode) and sendsServiceRequestwith required fields:
string type// service type to discoverMode mode// TCP or UDP response modeint 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 sendsServiceResponseover 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.
See DiscoveryTestCase for more information. Average discovery time in my home network is about 60 ms.
It's built with Maven:
mvn clean install
or
mvn clean install -DskipTests=true
to build without testing
See according Objective-C implementation: https://github.com/4ntoine/ServiceDiscovery-ios
Free for non-commercial usage, contact for commercial usage.
Anton Smirnov
dev [at] antonsmirnov [dot] name
2015