uPnP discovery suddenly stopp working?

I am trying this but it does not always work:

using Rssdp;
using System;

namespace Discovery {
  class Program {
    static void Main(string[] args) {
      SearchForDevices();
      Console.ReadKey();
    }

    public static async void SearchForDevices() {
      using (var deviceLocator = new SsdpDeviceLocator()) {
        var foundDevices = await deviceLocator.SearchAsync();

        foreach (var foundDevice in foundDevices) {
          Console.WriteLine("Found " + foundDevice.Usn + " at " + foundDevice.DescriptionLocation.ToString());
        }
      }
    }
  }
}

It only shows output for the first 3 runs or so. Then for the rest of the day I get nothing. I have checked the firewall settings in windows and allowed UDP in and out on all ports. Still the same. Not even sure how to debug.

I am running this from .NET Core Console App, in Windows 10.

[winkmichael]

Yes, good idea. I just did a super unscientific test and ran the UPNP discovery on my Ubiquiti, without knowing how the thing works, two observations; 1. Nothing appears in the list for at least 15 - 20 seconds, 2. The list of devices found populates over a several minute period.

[marchewek]

UDP packets’ delivery is not guaranteed - both broadcast message and response message can get lost in transfer. In general discovery should be treated as convenience improvement and implemented side-by-side with manual configuration. And since discovery can be used as a vector of DDoS attacks, I’d also recommend implementing possibility to turn discovery completely off (enabling/disabling firewall rule; I’d additionally restrict the rule to local LAN). If you want to see what is going on in the network, you could install any sniffing tool, e.g. Wireshark