AbstractSocketAppender.java

class AbstractSocketAppender extends ... 
     implements EventDispatcher, ExceptionHandler {

  private SocketConnectorFactory connectorFactory;
  private ConnectionRunner connectionRunner;
  private Future<?> runnerTask;

  public void start() {
    ...
    // extract method to create connector factory...
    connectorFactory = new DefaultSocketConnectorFactory();
    connectorFactory.setInetAddress(address);
    connectorFactory.setPort(port);
    connectorFactory.setDelayStrategy(...);
    connectorFactory.setExceptionHandler(this);

    // extract method to create connection runner...
    connectionRunner = new ConnectionRunner(connectorFactroy, this);
    connectionRunner.setContext(getContext());

    runnerTask = getContext().getExecutorService().submit(connectionRunner);
    ...
  }

  public void dispatchEvents(Socket socket) throws InterruptedException {
    ...
  }

}

ConnectionRunner.java

class ConnectionRunner extends ContextAwareBase implements Runnable {

  private final SocketConnectorFactory connectorFactory;
  private final EventDispatcher eventDispatcher;

  public final void run() {
    try {
      while (!Thread.currentThread().isInterrupted()) {
        SocketConnector connector = connectorFactory.createConnector();
        Future<Socket> socketFuture = getContext().getExecutorService().submit(connector);
        Socket socket = socketFuture.get();
        eventDispatcher.dispatchEvents(socket);   
      }
    } catch (InterruptedException ex) {
      assert true;   // ok... we'll exit now
    } catch (ExecutionException ex) {
      addError("connector error: " + ex);
    }
    addInfo("shutting down");
  }

}

One of the deficiencies in the existing tests of AbstractSocketAppender and SocketReceiver tests is the design prevents path testing in the run method. The tests use socket I/O to validate that events are being dispatched properly, but that's more of an integration test than a unit test, and is more fragile across platforms.