Fatal error: Uncaught RuntimeException: Failed to listen on "tcp://0.0.0.0:8081": Address already in use in /home/soh-works/www/websoket-sample/vendor/react/socket/src/TcpServer.php:172 Stack trace: #0 /home/soh-works/www/websoket-sample/vendor/react/socket/src/Server.php(77): React\Socket\TcpServer->__construct('tcp://0.0.0.0:8...', Object(React\EventLoop\StreamSelectLoop), Array) #1 /home/soh-works/www/websoket-sample/vendor/cboden/ratchet/src/Ratchet/Server/IoServer.php(59): React\Socket\Server->__construct('0.0.0.0:8081', Object(React\EventLoop\StreamSelectLoop)) #2 /home/soh-works/www/websoket-sample/bin/server.php(9): Ratchet\Server\IoServer::factory(Object(Ratchet\Http\HttpServer), 8081) #3 {main} thrown in /home/soh-works/www/websoket-sample/vendor/react/socket/src/TcpServer.php on line 172