使用套接字发送回复广播

Question

我试图发送广播，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();
    }

广播到达正常，但回复没有。没有抛出异常。谁能帮助我吗？我是否必须打开一个新连接才能回复或其他什么？

编辑：稍微改变了我的代码，现在它可以工作了！感谢您的回复！

Answer 1

看起来您的 SendBroadcast() 套接字没有绑定到端口，因此他不会接收任何内容。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) 将 SendBroadcast() 绑定到不同端口，并将 ReceiveBroadcast() 发送到该端口（而不是他自己的端口）端点 ep），或 (b) 让两个函数使用相同的套接字对象，以便它们都可以在端口 16789 上接收数据报。