client.addListener(callbackHandler, metadata);
// Get client side ServerThread pool.
Set callbackConnectors = client.getCallbackConnectors(callbackHandler);
Connector callbackConnector = (Connector) callbackConnectors.iterator().next();
SocketServerInvoker serverInvoker = (SocketServerInvoker) callbackConnector.getServerInvoker();
Field field = SocketServerInvoker.class.getDeclaredField("clientpool");
field.setAccessible(true);
LRUPool clientpool = (LRUPool) field.get(serverInvoker);
// Verify MicroSocketClientInvoker retries invocation after failure to get a connection.