Question

here is my code for the client

    class Program
{
    static void Main(string[] args)
    {
        string msg;
        Socket sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        IPEndPoint ep = new IPEndPoint(IPAddress.Parse("127.0.0.1"), 999);
        sck.Bind(ep);
        byte[] msgbytes;

        while (true)
        {
            msg = Console.ReadLine();
            msgbytes = ASCIIEncoding.ASCII.GetBytes(msg);
            sck.BeginSendTo(msgbytes, 0, msgbytes.Length, SocketFlags.None, ep, null, sck);
            Console.WriteLine("sent");
        }
    }

    void callBack(IAsyncResult result)
    {
        ((Socket)result.AsyncState).EndSendTo(result);
    }
}

}

and here is server code

    class Program
{
    static void Main(string[] args)
    {
        string msg;
        Socket sck = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
        IPEndPoint ep = new IPEndPoint(IPAddress.Any, 999);
        sck.Bind(ep);
        byte[] msgbytes = new byte[100];

        EndPoint client = (EndPoint)ep;

        int bytesrec;
        while (true)
        {
            bytesrec = sck.ReceiveFrom(msgbytes, 0, msgbytes.Length, SocketFlags.None, ref client);
            msg = ASCIIEncoding.ASCII.GetString(msgbytes);
            Console.WriteLine("4");
        }
    }
}

}

The problem is no packet is ever received by the server when i try sending with the client. The “4” is never written, which confirms sck.receivefrom executed.

Answer 1

In your client code change the following:
Instead of sck.Bind(ep); use sck.Connect(ep);
and instead of

sck.BeginSendTo(msgbytes, 0, msgbytes.Length, SocketFlags.None, ep, null, sck);

use

sck.Send(msgbytes, msgbytes.Length, SocketFlags.None);

and it should work…

edit:
if you really need to use async send… you can do something like:

IAsyncResult asyncres = sck.BeginSendTo(msgbytes, 0, msgbytes.Length, SocketFlags.None, ep, null, sck);
sck.EndSendTo(asyncres);