Socket.EndSendTo(IAsyncResult) Method


Ends a pending asynchronous send to a specific location.

 int EndSendTo(IAsyncResult ^ asyncResult);
 int EndSendTo(IAsyncResult ^ result);
public int EndSendTo (IAsyncResult asyncResult);
public int EndSendTo (IAsyncResult result);
member this.EndSendTo : IAsyncResult -> int
member this.EndSendTo : IAsyncResult -> int
Public Function EndSendTo (asyncResult As IAsyncResult) As Integer
Public Function EndSendTo (result As IAsyncResult) As Integer



An IAsyncResult that stores state information and any user defined data for this asynchronous operation.



If successful, the number of bytes sent; otherwise, an invalid Socket error.


asyncResult is null.

EndSendTo(IAsyncResult) was previously called for the asynchronous send.

An error occurred when attempting to access the socket.

The Socket has been closed.


The following code example ends an asynchronous send to a specific location.

StateObject^ so = safe_cast<StateObject^>(ar->AsyncState);
Socket^ s = so->workSocket;

int send = s->EndSendTo( ar );

Console::WriteLine( "The size of the message sent was : {0}", send );

StateObject so = (StateObject) ar.AsyncState;
Socket s = so.workSocket;

int send = s.EndSendTo(ar);

   Console.WriteLine("The size of the message sent was :" + send.ToString());

   Dim so As StateObject = CType(ar.AsyncState, StateObject)
   Dim s As Socket = so.workSocket
   Dim send As Integer = s.EndSendTo(ar)
   Console.WriteLine(("The size of the message sent was :" + send.ToString()))
End Sub


EndSendTo completes the asynchronous send operation started in BeginSendTo.

Before calling BeginSendTo, you need to create a callback method that implements the AsyncCallback delegate. This callback method executes in a separate thread and is called by the system after BeginSendTo returns. The callback method must accept the IAsyncResult returned by the BeginSendTo method as a parameter.

Within the callback method, call the AsyncState method of the IAsyncResult parameter to obtain the sending Socket. After obtaining the Socket, you can call the EndSendTo method to successfully complete the send operation and return the number of bytes sent.

If you are using a connectionless protocol, EndSendTo will block until the datagram is sent. If you are using a connection-oriented protocol, EndSendTo will block until the requested number of bytes are sent. There is no guarantee that the data you send will appear on the network immediately. To increase network efficiency, the underlying system may delay transmission until a significant amount of outgoing data is collected. A successful completion of the BeginSendTo method means that the underlying system has had room to buffer your data for a network send.


If you receive a SocketException, use the SocketException.ErrorCode property to obtain the specific error code. After you have obtained this code, refer to the Windows Sockets version 2 API error code documentation for a detailed description of the error.


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.

Applies to