How to brodcast discover a webserver on a special port

Question

I have a webserver running on a raspberry pi on port 7299, and I also have a .NET MAUI app which I want to discover the raspberry pi webserver from. The raspberry is kind of an IoT where I want to exchange some data between, how can I discover the device in a smart and fast way?

I have tried googling around and asked GPT, but I cannot figure out a smart way. I first tried a for loop with all the addresses in the network, but its really slow. I read somewhere that you maybe could do a "brodcast" and discover the device but I cannot figure out how to do it.

If it helps the webserver on the raspberry pi is running a docker container with a .NET MVC/API project.

Thanks for all ideas and help!

Best regards Max

Answer 1

I solved it the best way I could, and I think it works pretty fast, this is my current solution if no one else has a better idea:

public async Task DiscoverDeviceAsync()
        {
            string networkRange = "10.10.0.1-10.10.0.254"; 
            int port = 7299; 

            string[] ipRange = networkRange.Split('-');
            IPAddress startIPAddress = IPAddress.Parse(ipRange[0]);
            IPAddress endIPAddress = IPAddress.Parse(ipRange[1]);

            var tasks = new Task[endIPAddress.GetAddressBytes()[3] - startIPAddress.GetAddressBytes()[3] + 1];

            for (int i = 0; i < tasks.Length; i++)
            {
                byte[] ipBytes = startIPAddress.GetAddressBytes();
                ipBytes[3] += (byte)i;
                IPAddress currentIPAddress = new(ipBytes);
                tasks[i] = ScanIPAddress(currentIPAddress, port);
            }

            await Task.WhenAll(tasks);
        }

        async Task ScanIPAddress(IPAddress ipAddress, int port)
        {
            try
            {
                using TcpClient tcpClient = new();
                tcpClient.SendTimeout = 100;
                await tcpClient.ConnectAsync(ipAddress, port);
                Console.WriteLine($"Web server found at IP address: {ipAddress}");
                WebServerIp = ipAddress.ToString();
            }
            catch (SocketException ex)
            {
                Console.WriteLine(ex);
            }
        }