Finding all TCPListeners in a subnet listening on a specific port/Having all of them respond to a broadcast message

Question

I am trying to get all the TCPListener(s) of my application that are running on a specified port so I can display them in a server browser, I thought I could just send a udp packet to the broadcast with a message with the ip of the asking computer and have them respond to it once they see it. I don't want to manually go through all the possible ips in the subnet and try connect to them with a tcpclient at the specify port just to do it, I want them to respond to the message. Is that possible ? For reference the listener code looks like this:

       public async Task ListenAsync()
        {
            listener.Start();
            
            while (!_serverShouldClose)
            {
                var handleClientsTask = HandleClientsAsync();
                var sendAliveTask = SendAlive();
                if (listener.Pending())
                {
                    var clientTask = listener.AcceptTcpClientAsync();
                    var client = await clientTask;
                    await client.GetStream().WriteAsync(Encoding.UTF8.GetBytes("Hello from server\n"));
                    _connectedClients.Add(client);
                }
                await Task.WhenAll(sendAliveTask, handleClientsTask);
            }
            
            listener.Stop();
        }


        public async Task HandleClientsAsync()
        {
            byte[] buffer = new byte[1024];
            foreach (var client in _connectedClients)
            {
                if (!client.Connected)
                {
                    _connectedClients.Remove(client);
                    client.Close();
                    client.Dispose();
                    continue;
                }

                if(client.GetStream().DataAvailable)
                {
                    await client.GetStream().ReadAsync(buffer);
                    if (Encoding.ASCII.GetString(buffer).Contains("gib settings"))
                    {
                        await client.GetStream().WriteAsync(Encoding.ASCII.GetBytes(JsonSerializer.Serialize(_settings)));
                    }
                }
                
            }
        }

Answer 1

Is that possible ?

Technically, yes.

Personally, I would do this via Powershell or some other management-level solution like Windows Remote Management / WMI. That way you could just ask the OS directly, and then filter open sockets by port.