Problems with BeginReceive Callback
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Thread: Problems with BeginReceive Callback

  1. #1
    Join Date
    Aug 2012
    Posts
    6

    Problems with BeginReceive Callback

    Hi everybody

    I am dealing with a strange problem when closing a socket connection. I am using an asynchronous receive and I specified, as is MSDN's suggestion, a user-defined object as the last parameter in my BeginReceive(). I expect, as MSDN says, this same object to be passed in the State field of the IAsynchResult parameter of the Callback function I specified in my BeginReceive () call. But , as I close the connection, and the tcp layer as usual sends me a zero-length packet, the Callback function is called but the State field is the Socket native object which received the close and not the user-defined object I specified in the BeginReceive.
    This seems to be in contrast with MSDN specifications. What am I doing wrong ?

  2. #2
    Join Date
    Jan 2010
    Posts
    1,099

    Re: Problems with BeginReceive Callback

    Quote Originally Posted by towmtdj View Post
    Hi everybody
    Hi.
    Quote Originally Posted by towmtdj View Post
    What am I doing wrong ?
    Well, it would help if you posted some code - in particular, the call to BeginReceive(), and the corresponding callback method.
    Are you sure you've passed the right object and that you're checking in the right callback, or that there aren't any other methods invoking the same callback, possibly sending a Socket instead, and you don't expect it?

    Take a look at the MSDN example at this page.
    Here's the condensed version:
    Code:
    // some class that holds some user data, like the socket, or the buffer, and whatever
    public class StateObject
    {
         // ...
    }
    Code:
    // A listen callback, invoked by BeginAccept(), which passed a socket as user state object
    public static void Listen_Callback(IAsyncResult ar)
    {
         //...
         Socket s = (Socket) ar.AsyncState;        // retrieve the socket (normally, you know what type to cast to)
         Socket s2 = s.EndAccept(ar);                  // end operation, get the new socket
         StateObject state = new StateObject();    // create and init the StateObject instance
         state.workSocket = s2;
         s2.BeginReceive(so2.buffer, 0, StateObject.BUFFER_SIZE,0,
    	                       new AsyncCallback(Read_Callback), state);	// and pass it instead
    }
    Code:
    // the read callback retrieves the StateObject instance
    public static void Read_Callback(IAsyncResult ar)
    {
    	StateObject state = (StateObject) ar.AsyncState;
    	
    	//...
    }
    Last edited by TheGreatCthulhu; August 1st, 2012 at 07:36 AM.

  3. #3
    Join Date
    Aug 2012
    Posts
    6

    Re: Problems with BeginReceive Callback

    Hi TheGreatCThulhu, thank you for answering .

    I have to apologize 'cause I have just realized that I simply passed the wrong argument.
    Sorry for the annoyance, and thank you again.

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