If you want to use Zend Http Client locally on your computer on self signed domain without valid certificate, you can get error Unable to enable crypto on TCP connection make sure the "sslcafile" or "sslcapath" option are properly set for the environment. This can be solved by creating client with following options.

$options = array(
    'sslallowselfsigned' => true,
    'sslverifypeer' => false,
    'sslverifypeername' => false
);

$this->_httpClient = new \Zend\Http\Client(null, $options);
}