public abstract class HostInfo  {
    private static HostInfo _instance;
    public static HostInfo getInstance() {
        if (_instance == null) {
            _instance = ImplementationLoader.newInstance(HostInfo.class);
        }
        return _instance;
    }
    public void initialize() {
        init();
    }
    public String getHost() {
        return doGetHost();
    }
    public int getPort() {
        return doGetPort();
    }
    public String getContext() {
        return doGetContext();
    }
    protected abstract void init();
    protected abstract String doGetScheme();
    protected abstract String doGetHost();
    protected abstract int doGetPort();
    protected abstract String doGetContext();
    protected abstract void doSetScheme(final String scheme);
    protected abstract void doSetHost(final String host);
    protected abstract void doSetPort(final int port);
    protected abstract void doSetContext(final String context);
}

public class HostInfoImpl extends HostInfo {
	private String host;
	private int port;
	private String context;
	private String scheme;
 
	private HostInfoImpl getSessionSingletonInstance() {
		return SessionSingleton.getInstance(HostInfoImpl.class);
	}
	@Override
	protected String doGetHost() {
		String host = getSessionSingletonInstance().host;
		if (host == null) {
			throw new IllegalStateException("HostInfo is not initialized.");
		}
		return host;
	}
	@Override
	protected int doGetPort() {
		return getSessionSingletonInstance().port;
	}
	@Override
	protected void doSetHost(final String host) {
		getSessionSingletonInstance().host = host;
	}
	...
	@Override
	protected void init() {
		doSetHost(RWT.getRequest().getServerName());
		doSetPort(RWT.getRequest().getLocalPort());
		doSetContext(RWT.getRequest().getContextPath());
		doSetScheme(RWT.getRequest().getScheme());
	}
}

public class HostInfoImpl extends HostInfo {
    private String scheme = "http"; //$NON-NLS-1$
    private String host = "localhost"; //$NON-NLS-1$
    private String context = ""; //$NON-NLS-1$
 
    @Override
    protected String doGetHost() {
        return host;
    }
    @Override
    protected int doGetPort() {
        int port = Activator.getDefault().getServerPort();
        return port;
    }
    @Override
    protected void doSetHost(final String host) {
        this.host = host;
    }
    @Override
    protected void doSetPort(final int port) {
        // do nothing
    }
  ...
}
 
public class PortTrackerCustomizer implements ServiceTrackerCustomizer {
    private Integer httpPort = null;
...
    public Object addingService(final ServiceReference reference) {
        extractPort(reference);
        return context.getService(reference);
    }
    public void modifiedService(final ServiceReference reference, final Object service) {
        extractPort(reference);
    }
    private void extractPort(final ServiceReference reference) {
        // ignore if the help is starting
        if ("org.eclipse.help".equals(reference.getProperty("other.info"))) {return;} 
        try {
            // The http.port property is not defined if the ServletBridge is
            // used to load Equinox.
            Object httpPortObject = reference.getProperty("http.port"); 
            httpPort = Integer.parseInt(httpPortObject.toString());
        } catch (Exception ex) {
            // Do not throw exception - it will prevent the application from
            // starting when deployed with the ServletBridge.
            httpPort = null;
        }
 
    }
    public int getHttpPort() {
        if (httpPort == null) {
            throw new IllegalStateException("No OSGi HTTP Service running"); 
        }
        return httpPort;
    }
}
 
public class Activator extends AbstractUIPlugin {
...
	public void start(BundleContext context) throws Exception {
...
        portTrackerCustomizer = new PortTrackerCustomizer(context);
        portTracker = new ServiceTracker(context, HttpService.class.getName(), portTrackerCustomizer);
        portTracker.open();
	}
...
    public int getServerPort() {
        return portTrackerCustomizer.getHttpPort();
    }
}

public class DemoJettyCustomizer extends JettyCustomizer {
 
    @SuppressWarnings({ "rawtypes" })
    @Override
    public Object customizeHttpConnector(final Object connector, final Dictionary settings) {
        if (connector instanceof Connector) {
            Connector jettyConnector = (Connector)connector;
            jettyConnector.setPort(findFreePort());
        }
        return super.customizeHttpConnector(connector, settings);
    }
 
    private int findFreePort() {
        ServerSocket socket = null;
        try {
            socket = new ServerSocket(0);
            socket.setReuseAddress(true);
            return socket.getLocalPort();
        } catch (IOException e) {
            // ignore
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                   // ignore
                }
            }
        }
        return 0;
    }
}