whats the endpoint for ProtoOAApplicationAuthReq message?

I'm trying to send the payload from php for the message ProtoOAApplicationAuthReq like this:

        $content = json_encode([
            'payload' => [
                'clientId' => env('CTRADER_CLIENT_ID'),
                'clientSecret' => env('CTRADER_SECRET'),
            ]
        ]);
        $tuCurl = curl_init();
        curl_setopt($tuCurl, CURLOPT_URL, "live.ctraderapi.com");
        curl_setopt($tuCurl, CURLOPT_PORT, 5036);
        curl_setopt($tuCurl, CURLOPT_VERBOSE, 0);
        curl_setopt($tuCurl, CURLOPT_POSTFIELDS, $content);
        $tuData = curl_exec($tuCurl);

What am I doing wrong? Is that the right endpoint?