Update AxyncUdpConnection

Connection/AsyncUdpConnection.php

@@ -176,7 +176,7 @@ class AsyncUdpConnection extends UdpConnection
         if ($this->_contextOption) {
             $context = \stream_context_create($this->_contextOption);
             $this->_socket = \stream_socket_client("udp://{$this->_remoteAddress}", $errno, $errmsg,
-                30, STREAM_CLIENT_CONNECT, $context);
+                30, \STREAM_CLIENT_CONNECT, $context);
         } else {
             $this->_socket = \stream_socket_client("udp://{$this->_remoteAddress}", $errno, $errmsg);
         }