Php stream socket: The connection to wss://host:port was interrupted while the page was loading

Question

I am having issue with web socket connection/handshake from Firefox to my server written in Php. Problem is when I try to connect client(using js/php or even websocket.org/echo.html) I get issue and the issue is client is firstly connected and then disconnected automatically. And at server, I am using fwrite to to send message to client. And i have also noticed that for a client from firefox fwrite returns 0 as a response, but at client side I can see server has posted handshake data.

Now I see problem is here, when server is writing but response is 0 and still browser(firefox) is getting response but it gets disconnected with the server at the same time. I even tried to compare(calculate) data in bytes, which server is posting to client. I see its exactly same.

Note:- Just to mention here, same php server script is working fine for Opera/Chrome/Safari browsers.

Below are the things which are involved in this issue;

• Firefox [71.0]
• Php [7.0]
• Apache
• Let's Encrypt SSL

# STREAM SOCKET CREATION OVER SSL(WSS)
$context = stream_context_create(); 
stream_context_set_option($context, 'ssl', 'local_cert', 'ssl-test.pem'); #change to your own ssl.pem path
stream_context_set_option($context, 'ssl', 'allow_self_signed', true); 
stream_context_set_option($context, 'ssl', 'verify_peer', false); 
$sock = stream_socket_server("ssl://".HOST_NAME.":".PORT,$errno,$errstr,STREAM_SERVER_BIND|STREAM_SERVER_LISTEN, $context) or die('Unable to start server, seems server is already running!'); 
// stream_set_blocking($sock,TRUE);


# PUTTING ALL(CURRENT/UPCOMING) SOCKET CONNECTIONS IN ARRAY
$clients = array();

# INFINTE LOOP THOURGH ALL SOCKECT CURRENT/UPCOMING CONNECTIONS, SEND/RECEIVE DATA
while (true) {

    # ALL ACTIVE SOCKET CONNECTIONS
    $read = $clients;

    foreach($received_header as $key => $header){
        if($header['time']+1 < microtime(true)){
            $headers  = [];
            // echo $header['data'];
            $lines    = preg_split("/\r\n/", $header['data']);
            foreach($lines as $line) {
                $line = chop($line);
                if(preg_match('/\A(\S+): (.*)\z/', $line, $matches)){
                    $headers[$matches[1]] = $matches[2];
                }
            }
            $secKey     = $headers['Sec-WebSocket-Key'];
            $secAccept  = base64_encode(pack('H*', sha1($secKey . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11')));

            // create handshake header
            $upgrade  = "HTTP/1.1 101 Web Socket Protocol Handshake" .PHP_EOL.
            "Upgrade: websocket" .PHP_EOL.
            "Connection: Upgrade" .PHP_EOL.
            "Accept: text/html" .PHP_EOL.
            "Sec-WebSocket-Accept: $secAccept".PHP_EOL.PHP_EOL;

            // send handshake packet
            if(!fwrite($clients[$key], $upgrade)){
                file_put_contents('handshakes-est.txt', ($upgrade));
            }



            $handshakes[$key] = true;
            $unset_key = $key;
        }
    }
/* i have rest of the script here which do further communication after connection is setup */
}

Below are some screen-shots to better understand connection behavior issue on Firefox.

Headers during handshake:

Connection behavior over websocket: