WebSocketContainer container = ContainerProvider.getWebSocketContainer();

        Session connected = container.connectToServer(
                new Endpoint() {
                    @Override
                    public void onOpen(Session session, EndpointConfig endpointConfig) {
                        System.out.println("connected");
                    }
                },
                ClientEndpointConfig.Builder.create().build(),
                new URI("wss://echo.websocket.org"));
    }

Exception in thread "main" java.lang.IllegalArgumentException: XNIO000100: 'https' URL scheme chosen but no SSL provider given
	at org.xnio.http.HttpUpgrade$HttpUpgradeState.doUpgrade(HttpUpgrade.java:253)
	at org.xnio.http.HttpUpgrade$HttpUpgradeState.access$100(HttpUpgrade.java:165)
	at org.xnio.http.HttpUpgrade.performUpgrade(HttpUpgrade.java:129)
	at io.undertow.websockets.client.WebSocketClient$ConnectionBuilder.connect(WebSocketClient.java:214)
	at io.undertow.websockets.jsr.ServerWebSocketContainer.connectToServer(ServerWebSocketContainer.java:204)
	at Test.main(Test.java:22)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)