if (!channelFuture.isDone() || !channelFuture.isSuccess()) {
ConnectException cause = new ConnectException("Cannot connect to " + configuration.getAddress());
if (channelFuture.getCause() != null) {
cause.initCause(channelFuture.getCause());
}
throw cause;
}
Channel answer = channelFuture.getChannel();
// to keep track of all channels in use