是否可能有多个UDP C#套接字具有相同的LocalEndpoint？

Question

因此，我可以像为TCP套接字一样为每个客户端创建一个不同的UDP套接字吗？
注意：如果可能，请使用socket类来解释，而不是UDPClient类。

    private void SocketAsyncEventArgs_Completed(object sender, SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            switch (e.LastOperation)
            {
                case SocketAsyncOperation.Accept:
                case SocketAsyncOperation.Connect:
                    UDP.Bind(TCP.LocalEndPoint);

代码说明：我以为建立TCP连接（Connect/Accept）后可以在两边（客户机/服务器）绑定一个UDP套接字。对于服务器上只有一个客户机是很好的。对于新客户机，server会引发异常，因为它无法将多个套接字与一个localEndPoint绑定在一起。和客户端可以超过所有可用端口。所以我不能为每个客户端绑定一个UDP套接字到一个不同的localEndPoint。
我知道我可以创建一个唯一的UDP套接字并将接收消息传递给服务器上的相应客户端对象，但这有点麻烦。谢谢！

Answer 1

您可以针对唯一的源ip：port组合运行一个任务。这将允许您轻松地为每个唯一的传入源ip：port组合维护一个状态机。system.io.pipelines使将其绑定在一起变得非常容易。

首先设置一个类似于TCPListener的UdpListener任务，为每个新的ip：port升级一个任务以处理该端口，创建一个管道，并且每个时间的数据都来自该IPEndpoint，将数据放入PipeWriter

    static async Task StartUdpListener()
    {
        // Use a Dictionary to match packets from given connections to give Pipes
        ConcurrentDictionary<string, Pipe> connections = new ConcurrentDictionary<string, Pipe>();

        var udpServer = new UdpClient(new IPEndPoint(IPAddress.Any, 33000));
        while (true)
        {
            // Wait for some data to arrive
            var result = await udpServer.ReceiveAsync();

            if(connections.ContainsKey(result.RemoteEndPoint.ToString()))
            {
                // If we have seen this IPEndpoint before send the traffic to the pipe
                // the task associated with that Pipe willpick the traffic up
                connections.TryGetValue(result.RemoteEndPoint.ToString(), out var p);
                await p.Writer.WriteAsync(result.Buffer);
            }
            else
            {
                // If we have not seen it, make the pipe, stick the data in the pipe
                // and spin up a task to Read/Process the data
                var p = new Pipe();
                connections.TryAdd(result.RemoteEndPoint.ToString(), p);
                await p.Writer.WriteAsync(result.Buffer);
                _ = Task.Run(() => UdpServerClient(result.RemoteEndPoint.ToString(), p));
            }
        }
    }

这是内核在接收到TCPPacket时所做的操作的一个简单视图，它将其粘贴在套接字缓冲区中，供您通过流读取。

UDP服务器客户端任务如下所示：

    static async Task UdpServerClient(string serverName,Pipe p)
    {
        while (true)
        {
            var readResult = await p.Reader.ReadAsync();
            var message = Encoding.ASCII.GetString(readResult.Buffer.FirstSpan.ToArray());
            Console.WriteLine($"Server: {serverName} Received: {message}");
            p.Reader.AdvanceTo(readResult.Buffer.End);
        }
    }

为了完整起见，有几个客户机，它们通常在不同的机器上，但为了简单起见，我们将它们作为任务运行。

    static async Task UdpClientClient(string messageToSend)
    {
        var client = new UdpClient();
        client.Connect("127.0.0.1", 33000);
        for(var i=0;i<5;i++)
        {
            var message = ASCIIEncoding.ASCII.GetBytes(messageToSend + " #"+ i.ToString());
            await client.SendAsync(message, message.Length);
            await Task.Delay(1000);
        }
    }
}

将它们全部链接在一起：

    static async Task Main(string[] args)
    {
        _ = Task.Run(() => StartUdpListener());

        _ = UdpClientClient("hi Server!");
        _ = UdpClientClient("I am here server...");
        await UdpClientClient("Me too server!");
    }

Server: 127.0.0.1:53183 Received: Me too server! #0
Server: 127.0.0.1:53182 Received: I am here server... #0
Server: 127.0.0.1:53181 Received: hi Server! #0
Server: 127.0.0.1:53182 Received: I am here server... #1
Server: 127.0.0.1:53183 Received: Me too server! #1
Server: 127.0.0.1:53181 Received: hi Server! #1
Server: 127.0.0.1:53182 Received: I am here server... #2
Server: 127.0.0.1:53183 Received: Me too server! #2
Server: 127.0.0.1:53181 Received: hi Server! #2
Server: 127.0.0.1:53182 Received: I am here server... #3
Server: 127.0.0.1:53181 Received: hi Server! #3
Server: 127.0.0.1:53183 Received: Me too server! #3
Server: 127.0.0.1:53183 Received: Me too server! #4
Server: 127.0.0.1:53181 Received: hi Server! #4
Server: 127.0.0.1:53182 Received: I am here server... #4