Fatal error: Uncaught Error: Interface "Ratchet\RFC6455\Handshake\NegotiatorInterface" not found in /users/energydata/www/volkszaehler.org/vendor/ratchet/rfc6455/src/Handshake/ServerNegotiator.php:10 Stack trace: #0 {main} thrown in /users/energydata/www/volkszaehler.org/vendor/ratchet/rfc6455/src/Handshake/ServerNegotiator.php on line 10