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quantum32043
Asked:2024-05-02 01:38:46 +0000 UTC2024-05-02 01:38:46 +0000 UTC

C# 中的 UDP 广播仅适用于运行它的计算机

  • 772

有以下主机测试代码：

            string localIP = IP.ToString();

            UdpClient udpClient = new UdpClient();
            udpClient.EnableBroadcast = true;

            IPEndPoint broadcastEndPoint = new IPEndPoint(IPAddress.Parse("255.255.255.255"), 11000);

            try
            {
                var counter = 0;
                while (counter < 5)
                {
                    byte[] sendBytes = Encoding.ASCII.GetBytes(localIP);

                    udpClient.Send(sendBytes, sendBytes.Length, broadcastEndPoint);
                    counter++;
                    Thread.Sleep(5000);
                }
                
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
            finally
            {
                udpClient.Close();
            }

以及客户端的以下代码：

        UdpClient udpClient = new UdpClient(11000);
        string receivedData = null;
        try
        {
            IPEndPoint receiveEndPoint = new IPEndPoint(IPAddress.Any, 11000);
                byte[] receiveBytes = udpClient.Receive(ref receiveEndPoint);

                receivedData = Encoding.ASCII.GetString(receiveBytes);

                Console.WriteLine("Received broadcast from {0} : {1}\n",
                    receiveEndPoint.ToString(),
                    receivedData);
        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
        finally
        {
            udpClient.Close();
        }

当主机和客户端在同一台计算机上启动时，一切正常并且数据包到达客户端。但是，当我尝试在连接到同一本地网络的不同计算机上运行它们（手机上的调制解调器模式充当本地网络）时，数据包停止到达。两台机器上的防火墙都被禁用，所以我不知道问题是什么

我尝试将广播发送到较小的范围（192.255.255.255），但这也没有帮助。当您尝试调试客户端时，调试器将停止，并且程序将停止在 receiveData = Encoding.ASCII.GetString(receiveBytes) 行上显示任何生命迹象。我希望有人能提出解决方案

c#

1 个回答

  1. Best Answer

    我找到了解决问题的方法。事实证明，必须为单独使用的每个本地网络计算广播 IP。我只需获取本地网络地址及其掩码，用它来计算该网络的广播 IP 并向其发送 UDP 数据包。主机代码：

    IPEndPoint broadcastEndPoint = new IPEndPoint(Tools.GetBroadcastAddress(IP.ToString(), Tools.GetLocalMask().ToString()), 11000);
        try
        {
            ClientsWaiting = true;
            while (ClientsWaiting)
            {
                byte[] sendBytes = Encoding.ASCII.GetBytes(IP.ToString());
             udpClient.Send(sendBytes, sendBytes.Length, broadcastEndPoint);
                await Task.Delay(1000);
            }

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
        }
        finally
        {
            udpClient.Close();
        }

    获取地址方法代码：

    static class Tools
{
    public static IPAddress GetLocalAddress()
    {
        List<string> result = new List<string>();
        foreach (var networkInterface in NetworkInterface.GetAllNetworkInterfaces())
        {
            var items = networkInterface.GetIPProperties().UnicastAddresses
                .Where(x => x.Address.AddressFamily == AddressFamily.InterNetwork && IsInLocalRange(x.Address));
            result.AddRange(items.Select(ip => ip.Address.ToString()));
        }

        return IPAddress.Parse(result.Last());

        bool IsInLocalRange(IPAddress address)
        {
            byte[] bytes = address.GetAddressBytes();
            return bytes[0] == 192 && bytes[1] == 168;
        }
    }

    public static IPAddress GetLocalMask()
    {
        List<string> mask = new List<string>();
        foreach (var networkInterface in NetworkInterface.GetAllNetworkInterfaces())
        {
            var items = networkInterface.GetIPProperties().UnicastAddresses
                .Where(x => x.Address.AddressFamily == AddressFamily.InterNetwork && IsInLocalRange(x.Address));
            mask.AddRange(items.Select(ip => ip.IPv4Mask.ToString()));
        }

        return IPAddress.Parse(mask.Last());

        bool IsInLocalRange(IPAddress address)
        {
            byte[] bytes = address.GetAddressBytes();
            return bytes[0] == 192 && bytes[1] == 168;
        }
    }
    public static IPAddress GetBroadcastAddress(string ipAddress, string subnetMask)
    {
        if (string.IsNullOrEmpty(ipAddress) || string.IsNullOrEmpty(subnetMask))
        {
            throw new ArgumentException("IP address and subnet mask cannot be null or empty");
        }

        byte[] ipBytes = IPAddress.Parse(ipAddress).GetAddressBytes();
        byte[] maskBytes = IPAddress.Parse(subnetMask).GetAddressBytes();

        if (ipBytes.Length != maskBytes.Length)
        {
            throw new ArgumentException("Invalid IP address or subnet mask format");
        }

        byte[] broadcastBytes = new byte[ipBytes.Length];

        for (int i = 0; i < broadcastBytes.Length; i++)
        {
            broadcastBytes[i] = (byte)(ipBytes[i] | (byte)~maskBytes[i]);
        }

        return new IPAddress(broadcastBytes);
    }
}

    客户端代码：

    UdpClient udpClient = new UdpClient(11000);
        udpClient.EnableBroadcast = true;
        string receivedData = null;

            IPEndPoint receiveEndPoint = new IPEndPoint(IPAddress.Any, 0);
        while (true)
        {
            byte[] receiveBytes = udpClient.Receive(ref receiveEndPoint);

            receivedData = Encoding.ASCII.GetString(receiveBytes);

            Console.WriteLine($"Received broadcast from {receiveEndPoint.ToString()} : {receivedData}\n");
        }
    • 4

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