Aerys\Websocket\Rfc6455Endpoint::__invoke PHP Method

    public function __invoke(Request $request, Response $response, ...$args)
    {
        if ($request->getMethod() !== "GET") {
            $response->setStatus(HTTP_STATUS["METHOD_NOT_ALLOWED"]);
            $response->setHeader("Allow", "GET");
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        if ($request->getProtocolVersion() !== "1.1") {
            $response->setStatus(HTTP_STATUS["HTTP_VERSION_NOT_SUPPORTED"]);
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        $body = $request->getBody();
        if (!$body instanceof NullBody) {
            $response->setStatus(HTTP_STATUS["BAD_REQUEST"]);
            $response->setReason("Bad Request: Entity body disallowed for websocket endpoint");
            $response->setHeader("Connection", "close");
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        $hasUpgradeWebsocket = false;
        foreach ($request->getHeaderArray("Upgrade") as $value) {
            if (strcasecmp($value, "websocket") === 0) {
                $hasUpgradeWebsocket = true;
                break;
            }
        }
        if (empty($hasUpgradeWebsocket)) {
            $response->setStatus(HTTP_STATUS["UPGRADE_REQUIRED"]);
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        $hasConnectionUpgrade = false;
        foreach ($request->getHeaderArray("Connection") as $value) {
            $values = array_map("trim", explode(",", $value));
            foreach ($values as $token) {
                if (strcasecmp($token, "Upgrade") === 0) {
                    $hasConnectionUpgrade = true;
                    break;
                }
            }
        }
        if (empty($hasConnectionUpgrade)) {
            $response->setStatus(HTTP_STATUS["UPGRADE_REQUIRED"]);
            $response->setReason("Bad Request: \"Connection: Upgrade\" header required");
            $response->setHeader("Upgrade", "websocket");
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        if (!($acceptKey = $request->getHeader("Sec-Websocket-Key"))) {
            $response->setStatus(HTTP_STATUS["BAD_REQUEST"]);
            $response->setReason("Bad Request: \"Sec-Websocket-Key\" header required");
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        if (!in_array("13", $request->getHeaderArray("Sec-Websocket-Version"))) {
            $response->setStatus(HTTP_STATUS["BAD_REQUEST"]);
            $response->setReason("Bad Request: Requested Websocket version unavailable");
            $response->setHeader("Sec-WebSocket-Version", "13");
            $response->setHeader("Aerys-Generic-Response", "enable");
            $response->end();
            return;
        }
        $handshaker = new Handshake($response, $acceptKey);
        $onHandshakeResult = $this->application->onHandshake($request, $handshaker, ...$args);
        if ($onHandshakeResult instanceof \Generator) {
            $onHandshakeResult = (yield from $onHandshakeResult);
        }
        $request->setLocalVar("aerys.websocket", $onHandshakeResult);
        $handshaker->end();
    }