Fatal error: Uncaught Error: Interface 'Ratchet\RFC6455\Handshake\NegotiatorInterface' not found in /home/soh-works/www/websoket-sample/vendor/ratchet/rfc6455/src/Handshake/ServerNegotiator.php:10 Stack trace: #0 {main} thrown in /home/soh-works/www/websoket-sample/vendor/ratchet/rfc6455/src/Handshake/ServerNegotiator.php on line 10