为使用持久连接的 API 编写套接字服务器

我被要求创建一个应用程序来管理通常位于 NAT 或防火墙后面的设备，因此无法从外部访问。

幸运的是，该设备的创建者想到了这一点，所以他们创建了一个 API，可以连接到外部服务器并保持连接有效，同时还可以通过同一连接接收请求 - 如果我理解手册的话。 有问题的设备是 Videosec 人脸识别设备，协议称为“LAPI”（v1 或 v2），我能找到的有关该协议的所有信息都在这里：http ://videosec.com/support/Firmware/oet/OET-213H_API-JSON.pdf

不幸的是，它不起作用。我一打开设备就收到了心跳请求，但我不知道它是否确认了我的 HTTP 200 响应，而且我发送的任何请求都没有得到满足——只是被设备忽略，并不断发送心跳。

我的问题是 - 我这样做对吗？我是否足够了解 HTTP 保持活动（持久）连接？这是我的服务器套接字代码。它是用 PHP 编写的，但我也尝试过 Python：

<?php
header_remove();
$host = "(public ip)";
$port = 5196;
set_time_limit(0);

if (!extension_loaded('sockets')) {
    die('The sockets extension is not loaded.');
}

$socket = socket_create(AF_INET, SOCK_STREAM, 0) or die("Could not create socket\n");
$result = socket_bind($socket, $host, $port) or die("Could not bind to socket\n");
$result = socket_listen($socket, 3) or die("Could not set up socket listener\n");

function getLocalTime()
{
        $dt = new DateTime("now", new DateTimeZone('Europe/Belgrade'));
        return $dt->format('Y-m-d H:i:s');
}

function returnok($spawn, $url = "/LAPI/V1.0/PACS/Controller/HeartReportInfo")
{
        $rsobj = [
                "ResponseURL" => $url,
                "Code" => 0,
                "Data" => [
                        "Time" => getLocalTime()
                ]
        ];
        $resobj = json_encode($rsobj, JSON_UNESCAPED_SLASHES) . PHP_EOL;
        $response = "HTTP/1.1 200 Ok" . PHP_EOL;
        $response.= "Content-Length: " . strlen($resobj) . PHP_EOL;
        $response.= "Content-Type: application/json" . PHP_EOL;
        $response.= "Connection: keep-alive" . PHP_EOL;
        $response.= "X-Frame-Options: SAMEORIGIN" . PHP_EOL;
        $response.= $resobj . PHP_EOL;
        echo $response;
        if (!socket_write($spawn, $response, strlen($response))) {
                echo "Could not write output\n";
        }
}

function writeback($spawn, $url, $method = "GET")
{
        $output = $method . " " . $url . " HTTP/1.1" . PHP_EOL;
        $output.= "Content-Type: application/json" . PHP_EOL;
        $output.= "Connection: keep-alive" . PHP_EOL;
        $output.= PHP_EOL;
        echo $output;
        if (!socket_write($spawn, $output, strlen($output))) {
                echo "Could not write output\n";
        }
}

$spa = true;
while ($spa) {
        $spawn = socket_accept($socket) or die("Could not accept incoming connection\n");
        if ($input = socket_read($spawn, 16 * 1048576)) {
                $input = trim($input);
                if ($spawn) {
                        returnok($spawn);
                        sleep(7);
                        writeback($spawn, "/LAPI/V1.0/PeopleLibraries/BasicInfo");
                } else {
                        $spa = false;
                }
        }
    socket_close($spawn);
}

socket_close($socket);
?>

交换的内容如下：

RECV: POST /LAPI/V1.0/PACS/Controller/HeartReportInfo HTTP/1.1
Host: (redacted):5196
Content-Type: application/json
Content-Length: 180
Connection: keep-alive

{
"RefId": "(redacted)",
"Time": "2011-12-01 00:38:07",
"NextTime": "2011-12-01 00:38:37",
"DeviceCode": "(redacted)",
"DeviceType": 1
}

SEND: HTTP/1.1 200 OK
Content-Length: 108
Content-Type: application/json
Connection: keep-alive
X-Frame-Options: SAMEORIGIN
{"ResponseURL":"/LAPI/V1.0/PACS/Controller/HeartReportInfo","Code":0,"Data":{"Time":"2024-11-26 02:09:06"}}

SEND: GET /LAPI/V1.0/PeopleLibraries/BasicInfo HTTP/1.1
Content-Type: application/json
Connection: keep-alive

RECV: POST /LAPI/V1.0/PACS/Controller/HeartReportInfo HTTP/1.1
Host: (redacted):5196
Content-Type: application/json
Content-Length: 180
Connection: keep-alive

{
"RefId": "(redacted)",
"Time": "2011-12-01 00:38:16",
"NextTime": "2011-12-01 00:38:46",
"DeviceCode": "(redacted)",
"DeviceType": 1
}

SEND: HTTP/1.1 200 OK
Content-Length: 108
Content-Type: application/json
Connection: keep-alive
X-Frame-Options: SAMEORIGIN
{"ResponseURL":"/LAPI/V1.0/PACS/Controller/HeartReportInfo","Code":0,"Data":{"Time":"2024-11-26 02:09:15"}}