How to use cUrl and WebSocket: https://www.youtube.com/watch?v=NLIhd0wYO24&ab_channel=DanielStenberg

Connecting to WebSocket via PHP and cURL. Connection is successful and the connection speed is good. First chunk of frames of 1024B is taken fine, second one (774B) arrived as expected. Then getting error #23 “Failure writing output to destination” and connection is interrupted. I am returning same content length for both chunks/frames. I am not able to send “HeartBeat” to keep the connection alive as well.
I also tried to Win 10, XAMPP, PHP 8.2, cUrl verion 8.3.0 in CLI mode with local admin rights. Identical result. Tried with root sudo user. Same.

// URL and parameters
$url = 'https://www.example.com/?example_param=xxxx-xxxx';
$accessToken = 'xxxxxxxxxxx';
$webSocketKey = 'lSZolfGbvpepiTeZzjGomg==';

// Headers
$headers = [
    'Upgrade: websocket',
    'Connection: Upgrade',
    'Authorization: Bearer ' . $accessToken,
    'Sec-WebSocket-Key: ' . $webSocketKey,
    'Sec-WebSocket-Version: 13',
];

// cURL initialization
echo 'Init...START' . PHP_EOL;
$ch = curl_init();
echo 'Init...END' . PHP_EOL;

$outputJsonFile = __DIR__ . DIRECTORY_SEPARATOR . '_json.log';
$outputFile = __DIR__ . DIRECTORY_SEPARATOR . '_data.log';
$fileHandle = fopen($outputFile, 'w');
if ($fileHandle === false) {
    trigger_error('File err', E_USER_ERROR);
}

$objThis = new stdClass();
$objThis->result = '';
$objThis->strLen = 0;
$objThis->readCalls = 0;
$objThis->headers = '';

$callback = function ($ch, $str) use (&$objThis)
{
    // $objThis->result .= $str;
    $strTmp = trim(preg_replace('/[[:^print:]]/', '', $str), '~'); // should be aA
    // $strTmp = trim($str, "x00xff");

    $objThis->result .= $strTmp;

    $strLen = mb_strlen($str, '8bit'); // Same as strlen()

    $objThis->strLen += $strLen;

    echo PHP_EOL . '$result(cleaned)=' . (int)strlen($objThis->result) . PHP_EOL;
    echo PHP_EOL . '$str[' . mb_strlen($str) . '-' . mb_strlen($str, '8bit') . '-' . $strLen . ']=' . (int)strlen($str) . PHP_EOL;
    echo PHP_EOL . '$callback=' . $strTmp . PHP_EOL;

    return $objThis->strLen; //return the exact length
};

$callbackRead = function ($ch, $fh, $length) use (&$objThis)
{
    $objThis->readCalls++;
    return fread($fh, $length); // return 'PING';
};

$callbackHeader = function ($ch, $headerLine) use (&$objThis)
{
    $objThis->headers .= $headerLine;
    if (trim($headerLine) === 'Upgrade: websocket') {
        echo PHP_EOL . '#Connected!#' . PHP_EOL;
    }

    return strlen($headerLine);
};

$fR = tmpfile();
fwrite($fR, 'HeartBeat');
// Reset the file pointer
fseek($fR, 0);

// Set cURL options
$rO = curl_setopt_array($ch, [
    CURLOPT_URL => $url,
    CURLOPT_RETURNTRANSFER => true, // Return response as string
    CURLOPT_HTTPHEADER => $headers,
    CURLOPT_VERBOSE => true, // Verbose output
    CURLOPT_BUFFERSIZE => 10485760, //  receive buffer size 3 MB = 3145728 Bytes (in binary) 10 MB = 10485760 Bytes (in binary)
    // CURLOPT_WRITEDATA => $ch, // Not supported by PHP

    // CURLOPT_FILE => $fileHandle,
    CURLOPT_FOLLOWLOCATION => true,
    CURLOPT_FAILONERROR => true,
    CURLOPT_FORBID_REUSE => true,
    CURLOPT_FRESH_CONNECT => true,
    // CURLOPT_PUT => true, // Not appropriate for the case
    CURLOPT_HEADERFUNCTION => $callbackHeader, //
    CURLOPT_INFILE => $fR, // CallBack
    CURLOPT_INFILESIZE => mb_strlen('HeartBeat', '8bit'), // size
    CURLOPT_READFUNCTION => $callbackRead, // CallBack read
    CURLOPT_WRITEFUNCTION => $callback, // CallBack write
]);

echo PHP_EOL . 'Set cURL options' . PHP_EOL; var_dump($rO); PHP_EOL;

echo 'Exec...START' . PHP_EOL;
// Execute cURL request
$response = curl_exec($ch);
echo 'Exec...END' . PHP_EOL;

// Check for errors
if ($response === false) {
    echo 'cURL error [#' . curl_errno($ch) . ']: ' . curl_error($ch);
} else {
    // Output response
    echo 'Response: ' . $response;
}

// Close cURL handle
curl_close($ch);
fclose($fileHandle);

rewind($fR);
$tmlFile = stream_get_contents($fR);
fclose($fR);

$jTxt = json_decode($objThis->result);
$jP = json_encode($jTxt, JSON_PRETTY_PRINT);
file_put_contents($outputJsonFile, $jP);

echo PHP_EOL . 'readCalls: ' . $objThis->readCalls . PHP_EOL;
echo PHP_EOL . '$tmlFile: ' . $tmlFile . PHP_EOL;
echo PHP_EOL . 'result: ' . $jP . PHP_EOL;

die('.....................');

I tried to set message result listener and I was expecting to be able to receive/send messages to both directions.