/**
* Send handshake HTTP/1.1 response to the client to enable protocol switching.
*
* @param BufferedDuplexStreamInterface $socket
* @param HttpRequest $request
*/
protected function sendHandshake(BufferedDuplexStreamInterface $socket, HttpRequest $request) : \Generator
{
$accept = base64_encode(sha1($request->getHeaderLine('Sec-WebSocket-Key') . self::GUID, true));
$message = sprintf("HTTP/%s 101 Switching Protocols\r\n", $request->getProtocolVersion());
$message .= "Connection: Upgrade\r\n";
$message .= "Upgrade: websocket\r\n";
$message .= sprintf("Sec-WebSocket-Accept: %s\r\n", $accept);
$message .= "Sec-WebSocket-Version: 13\r\n";
$message .= "\r\n";
yield from $socket->write($message);
}
