💎 C# / .NET 对接

using System;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class LicenseClient
{
    const string API_BASE = "https://你的域名";
    const string USERNAME = "你的用户名";
    const string APP_NAME = "a";
    const string APP_KEY  = "32位程序密钥";

    static string Md5Sign(string act, string card, string mac, string app, long ts, string key)
    {
        var raw = $"{act}|{card}|{mac}|{app}|{ts}|{key}";
        using var md5 = MD5.Create();
        var bytes = md5.ComputeHash(Encoding.UTF8.GetBytes(raw));
        var sb = new StringBuilder();
        foreach (var b in bytes) sb.Append(b.ToString("x2"));
        return sb.ToString();
    }

    static async Task Call(string act, string card, string mac)
    {
        long ts = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
        string sign = Md5Sign(act, card, mac, APP_NAME, ts, APP_KEY);
        var url = $"{API_BASE}/kami/{USERNAME}/check.php" +
                  $"?act={act}&app={APP_NAME}&card={card}" +
                  $"&mac={mac}&sign={sign}&ts={ts}";

        using var http = new HttpClient();
        return await http.GetStringAsync(url);
    }

    static async Task Main()
    {
        string card = "ABCD-EFGH-JKLM-NPQR";
        string mac  = "MACHINE-CODE-HERE";

        // 登录
        var resp = await Call("login", card, mac);
        Console.WriteLine(resp);

        // 心跳循环
        while (true)
        {
            await Task.Delay(TimeSpan.FromSeconds(55));
            var r = await Call("heartbeat", card, mac);
            if (!r.Contains("\"code\":0")) { Console.WriteLine("心跳失败"); break; }
        }
    }
}