eSTK.me firmware backup

<?php

function send_packet($socket, $tag, $value)
{
    $packet = "";
    $packet .= pack('C', $tag);
    $packet .= pack('v', strlen($value));
    $packet .= $value;
    return stream_socket_sendto($socket, $packet);
}

function read_packet($socket, &$tag, &$value)
{
    $buffer = stream_socket_recvfrom($socket, 1);
    $tag = unpack('C', $buffer)[1];
    $buffer = stream_socket_recvfrom($socket, 2);
    $length = unpack('v', $buffer)[1];
    $value = "";
    while (strlen($value) < $length) {
        $value .= stream_socket_recvfrom($socket, $length - strlen($value));
    }
}

$socket = stream_socket_server("tcp://0.0.0.0:1888");

while (1) {
    $accepted = stream_socket_accept($socket, null, $peername);
    if (!$accepted) {
        continue;
    }

    echo "Accepted client: {$peername}" . PHP_EOL;

    send_packet($accepted, 0x01, "{$peername}, Welcome to RemoteLPA server");

    while (1) {
        echo "lpac> ";
        $cmd = fgets(STDIN);
        $proc = proc_open("./lpac {$cmd}", [['pipe', 'r'], ['pipe', 'w'], ['pipe', 'w']], $pipes, ".", ["APDU_INTERFACE" => "./libapduinterface_stdio.so"]);

        while (1) {
            $read = [$pipes[1], $accepted];
            $write = null;
            $exception = null;

            $res = stream_select($read, $write, $exception, null);

            if (in_array($pipes[1], $read)) {
                $data = fgets($pipes[1]);
                $request = json_decode($data, true);
                if (!$request) {
                    continue;
                }

                switch ($request['type']) {
                    case 'apdu':
                        switch ($request['payload']['func']) {
                            case 'connect':
                                fwrite($pipes[0], json_encode(['type' => 'apdu', 'payload' => ['ecode' => 0]]) . PHP_EOL);
                                break;
                            case 'logic_channel_open':
                                fwrite($pipes[0], json_encode(['type' => 'apdu', 'payload' => ['ecode' => 0]]) . PHP_EOL);
                                break;
                            case 'transmit':
                                send_packet($accepted, 0x02, hex2bin($request['payload']['param']));
                                break;
                        }
                        break;
                    case 'lpa':
                        print_r($request);
                        proc_close($proc);
                        break 2;
                    default:
                        print_r($request);
                        break;
                }
            }

            if (in_array($accepted, $read)) {
                read_packet($accepted, $tag, $value);
                fwrite($pipes[0], json_encode(['type' => 'apdu', 'payload' => ['ecode' => 0, 'data' => bin2hex($value)]]) . PHP_EOL);
            }
        }
    }
}