IT-Nexus/agent-cs/Services/RtcService.cs

using System.Drawing;
using System.Drawing.Imaging;
using System.Net.WebSockets;
using System.Text;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace ITNexusAgent.Services;

// Überträgt den Bildschirm via JPEG-Frames über WebSocket an den Browser
public class RtcService
{
    private readonly string _serverUrl;
    private readonly string _agentKey;
    private readonly string _hostname;

    private static readonly ImageCodecInfo JpegCodec =
        ImageCodecInfo.GetImageEncoders().First(c => c.FormatID == ImageFormat.Jpeg.Guid);

    public RtcService(string serverUrl, string agentKey, string hostname)
    {
        _serverUrl = serverUrl;
        _agentKey = agentKey;
        _hostname = hostname;
    }

    public async Task RunAsync(CancellationToken ct)
    {
        while (!ct.IsCancellationRequested)
        {
            try { await ConnectAsync(ct); }
            catch (Exception ex) { AgentWorker.Log($"RDP: {ex.Message}"); }

            if (!ct.IsCancellationRequested)
                await Task.Delay(TimeSpan.FromSeconds(15), ct).ContinueWith(_ => { });
        }
    }

    private async Task ConnectAsync(CancellationToken ct)
    {
        var wsUrl = _serverUrl
            .Replace("https://", "wss://")
            .Replace("http://", "ws://")
            + $"/ws?type=rdp-agent&key={Uri.EscapeDataString(_agentKey)}&hostname={Uri.EscapeDataString(_hostname)}";

        using var ws = new ClientWebSocket();
        await ws.ConnectAsync(new Uri(wsUrl), ct);
        AgentWorker.Log("RDP: Bereit");

        CancellationTokenSource? captureCts = null;

        var buf = new byte[4096];
        while (ws.State == WebSocketState.Open && !ct.IsCancellationRequested)
        {
            WebSocketReceiveResult res;
            try { res = await ws.ReceiveAsync(new ArraySegment<byte>(buf), ct); }
            catch { break; }

            if (res.MessageType == WebSocketMessageType.Close) break;

            var raw = Encoding.UTF8.GetString(buf, 0, res.Count);
            JObject? obj;
            try { obj = JObject.Parse(raw); } catch { continue; }

            var type = obj["type"]?.ToString();

            if (type == "rdp_start" && captureCts == null)
            {
                captureCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
                _ = CaptureLoopAsync(ws, captureCts.Token);
                AgentWorker.Log("RDP: Screen-Capture gestartet");
            }
            else if (type == "rdp_stop" && captureCts != null)
            {
                captureCts.Cancel();
                captureCts = null;
                AgentWorker.Log("RDP: Screen-Capture gestoppt");
            }
        }

        captureCts?.Cancel();
        AgentWorker.Log("RDP: Getrennt");
    }

    private static async Task CaptureLoopAsync(ClientWebSocket ws, CancellationToken ct)
    {
        var encParams = new EncoderParameters(1);
        encParams.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 60L);

        while (!ct.IsCancellationRequested && ws.State == WebSocketState.Open)
        {
            try
            {
                var screen = System.Windows.Forms.Screen.PrimaryScreen;
                if (screen == null) { await Task.Delay(500, ct).ContinueWith(_ => { }); continue; }

                var bounds = screen.Bounds;
                using var bmp = new Bitmap(bounds.Width, bounds.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
                using (var g = Graphics.FromImage(bmp))
                    g.CopyFromScreen(bounds.X, bounds.Y, 0, 0, bounds.Size);

                byte[] jpeg;
                using (var ms = new MemoryStream())
                {
                    bmp.Save(ms, JpegCodec, encParams);
                    jpeg = ms.ToArray();
                }

                var payload = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(new
                {
                    type = "rdp_frame",
                    data = Convert.ToBase64String(jpeg),
                    w = bounds.Width,
                    h = bounds.Height
                }));

                if (ws.State == WebSocketState.Open)
                    await ws.SendAsync(new ArraySegment<byte>(payload), WebSocketMessageType.Text, true, CancellationToken.None);
            }
            catch (OperationCanceledException) { break; }
            catch (Exception ex) { AgentWorker.Log($"RDP: Capture-Fehler: {ex.Message}"); }

            // ~8 fps
            await Task.Delay(125, ct).ContinueWith(_ => { });
        }
    }
}