Connecting two UDP clients to one port (Send and R

问题:

I tried the suggestion from this question with very little success.

Please... any help will be greatly appreciated!

Here is my code:

static void Main(string[] args)
{

    IPEndPoint localpt = new IPEndPoint(IPAddress.Any, 6000);

    UdpClient udpServer = new UdpClient(localpt); 
    udpServer.Client.SetSocketOption(
        SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

    UdpClient udpServer2 = new UdpClient();
    udpServer2.Client.SetSocketOption(
        SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

    udpServer2.Client.Bind(localpt); // <<---------- Exception here
}

回答1:

You have to set the socket option before binding.

    static void Main(string[] args)
    {
        IPEndPoint localpt = new IPEndPoint(IPAddress.Any, 6000);

        UdpClient udpServer = new UdpClient();
        udpServer.Client.SetSocketOption(
            SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
        udpServer.Client.Bind(localpt);

        UdpClient udpServer2 = new UdpClient();
        udpServer2.Client.SetSocketOption(
            SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

        udpServer2.Client.Bind(localpt); // <<---------- No Exception here

        Console.WriteLine("Finished.");
        Console.ReadLine();
    }

Or a more illustrative example:

    static void Main(string[] args)
    {
        IPEndPoint localpt = new IPEndPoint(IPAddress.Loopback, 6000);

        ThreadPool.QueueUserWorkItem(delegate
        {
            UdpClient udpServer = new UdpClient();
            udpServer.ExclusiveAddressUse = false;
            udpServer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
            udpServer.Client.Bind(localpt);

            IPEndPoint inEndPoint = new IPEndPoint(IPAddress.Any, 0);
            Console.WriteLine("Listening on " + localpt + ".");
            byte[] buffer = udpServer.Receive(ref inEndPoint);
            Console.WriteLine("Receive from " + inEndPoint + " " + Encoding.ASCII.GetString(buffer) + ".");
        });

        Thread.Sleep(1000);

        UdpClient udpServer2 = new UdpClient();
        udpServer2.ExclusiveAddressUse = false;
        udpServer2.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
        udpServer2.Client.Bind(localpt);

        udpServer2.Send(new byte[] { 0x41 }, 1, localpt);

        Console.Read();
    }

回答2:

I looked up your error message and this explains what the error is and why it is happening.

Here is the exact error message and reason WSAEACCES 10013 (MSDN)

Permission denied.

An attempt was made to access a socket in a way forbidden by its access permissions. An example is using a broadcast address for sendto without broadcast permission being set using setsockopt(SO_BROADCAST).

Another possible reason for the WSAEACCES error is that when the bind function is called (on Windows NT 4.0 with SP4 and later), another application, service, or kernel mode driver is bound to the same address with exclusive access. Such exclusive access is a new feature of Windows NT 4.0 with SP4 and later, and is implemented by using the SO_EXCLUSIVEADDRUSE option.

回答3:

Even changing your code so that I can pass in an IP address I gets the same error message it appears that you can't bind to the same port and only one port can be used here is the sample code I used your example and Altered it to capture my ip from my local machine..

        IPAddress ipAddress = Dns.Resolve(Dns.GetHostName()).AddressList[0];
        IPEndPoint ipLocalEndPoint = new IPEndPoint(ipAddress, 11000);

        //IPEndPoint localpt = new IPEndPoint(ipLocalEndPoint);

        UdpClient udpServer = new UdpClient(ipLocalEndPoint);
        udpServer.Client.SetSocketOption(
            SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
        udpServer.Connect(ipLocalEndPoint);
        UdpClient udpServer2 = new UdpClient();
        udpServer2.Client.SetSocketOption(
            SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);

        udpServer2.Client.Bind(ipLocalEndPoint); // <<---------- Exception here

this will produce the exception on the Bind () method.. sorry.

回答4:

To solve WSAEACCESS 10013 (MSDN) exception in UDP application you can try

udpServer.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.Broadcast, true);