在 ubuntu 上时，无法使用 .NET Core 在局域网上发送唤醒

Question

我正在尝试从 .NET Core MVC 应用程序发送局域网唤醒数据包。

如果应用程序托管在 Windows 主机上，它可以完美运行，但是当它在我的 Raspberry Pi 3（使用 Ubuntu Mate）上运行时，我收到以下错误：

fail: Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware[0]
An unhandled exception has occurred: Permission denied 255.255.255.255:40000
System.Net.Internals.SocketExceptionFactory+ExtendedSocketException (0x80004005): Permission denied 255.255.255.255:40000
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.Sockets.Socket.Connect(EndPoint remoteEP)
at System.Net.Sockets.Socket.Connect(IPAddress address, Int32 port)

我正在使用它来发送 WOL 数据包：

public static bool WakeUp(string macAddress)
    {
        bool retVal = false;
        try
        {
            byte[] mac = null;

            // Parse string to byte array
            string[] macDigits = null;
            if (macAddress.Contains("-"))
            {
                macDigits = macAddress.Split('-');
            }
            else
            {
                macDigits = macAddress.Split(':');
            }

            if (macDigits.Length != 6)
            {
                //incorrect MAC address
            }
            else
            {
                mac = macDigits.Select(s => Convert.ToByte(s, 16)).ToArray();
            }

            if (mac != null)
            {

                // WOL packet is sent over UDP 255.255.255.0:40000.
                UdpClient client = new UdpClient();
                client.Client.Connect(IPAddress.Broadcast, 40000);

                // WOL packet contains a 6-bytes trailer and 16 times a 6-bytes sequence containing the MAC address.
                byte[] packet = new byte[17 * 6];

                // Trailer of 6 times 0xFF.
                for (int i = 0; i < 6; i++)
                    packet[i] = 0xFF;
                // Body of magic packet contains 16 times the MAC address.
                for (int i = 1; i <= 16; i++)
                    for (int j = 0; j < 6; j++)
                        packet[i * 6 + j] = mac[j];

                // Submit
                int result = client.Client.Send(packet);
                if (result > 0)
                {
                    retVal = true;
                }
            }
        }
        catch (Exception ex)
        {
            throw;
        }

        return retVal;
    }

出于测试目的，我将端口更改为 2050 -> 相同的错误。

以防万一，这是 Program.cs 的内容

public class Program
    {
        public static void Main(string[] args)
        {
            BuildWebHost(args).Run();
        }

        public static IWebHost BuildWebHost(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .UseKestrel()
            .UseUrls("http://*:80")
            .UseContentRoot(Directory.GetCurrentDirectory())
            .Build();
    }

知道这是什么原因吗？应用程序的其余部分按预期工作。

Answer 1

启用广播后它对我有用：

// UdpClient client = new UdpClient();
client.EnableBroadcast = true;