c# - 使用 Socket 发送对广播的回复

Question

我正在尝试发送一个广播，然后让服务器回复它:

public static void SendBroadcast()
    {
        byte[] buffer = new byte[1024];
        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, 1);

        socket.Connect(new IPEndPoint(IPAddress.Broadcast, 16789));
        socket.Send(System.Text.UTF8Encoding.UTF8.GetBytes("Anyone out there?"));

        var ep = socket.LocalEndPoint;

        socket.Close();

        socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

        socket.Bind(ep);
        socket.Receive(buffer);
        var data = UTF8Encoding.UTF8.GetString(buffer);
        Console.WriteLine("Got reply: " + data);

        socket.Close();
    }

    public static void ReceiveBroadcast()
    {
        byte[] buffer = new byte[1024];

        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        var iep = new IPEndPoint(IPAddress.Any, 16789);
        socket.Bind(iep);

        var ep = iep as EndPoint;
        socket.ReceiveFrom(buffer, ref ep);
        var data = Encoding.UTF8.GetString(buffer);

        Console.WriteLine("Received broadcast: " + data + " from: " + ep.ToString());

        buffer = UTF8Encoding.UTF8.GetBytes("Yeah me!");
        socket.SendTo(buffer, ep);

        socket.Close();
    }

广播正常到达，但回复没有。不会抛出异常。谁能帮我？我是否必须为回复或其他内容打开一个新连接？

编辑:稍微更改了我的代码，现在可以使用了!感谢您的回复!

Answer 1

您的 SendBroadcast() 套接字似乎没有绑定(bind)到端口，因此他不会收到任何东西。事实上，您的 ReceiveBroadcast() 套接字正在将回复发送回他自己的端口，因此他将收到他自己的回复。

ReceiveBroadcast: binds to port 16789
SendBroadcast:    sends to port 16789
ReceiveBroadcast: receives datagram on port 16789
ReceiveBroadcast: sends reply to 16789
ReceiveBroadcast: **would receive own datagram if SendTo follwed by Receive**

您需要 (a) SendBroadcast() 绑定(bind)到一个不同的端口并更改 ReceiveBroadcast() 发送到那个端口(而不是他自己的端点 ep)，或者 (b) 让两个函数使用同一个套接字对象，这样它们就可以都在端口 16789 上接收数据报。